LIBRARY OF THE 
 
 UNIVERSITY OF ILLINOIS 
 
 AT URBANA-CHAMPAIGN 
 
 510.8 
 
 XX(or 
 
 no. 547-5 5 Z 
 cop- 2. 
 
beiow v efore the ife? * mi £*"'* to 
 
 2 7996 
 
 aae *teid 0w 
 
Digitized by the Internet Archive 
 in 2013 
 
 http://archive.org/details/etsstudentsguide547davi 
 
5/a w 
 
 (ML 
 
 uiucDc;s-R-72-5 1 t-T 
 
 THE LIBRARY GB THE 
 
 OCT 2 6 1972 
 
 UNIVERSITY OF ILLINOIS 
 AT URBANA-CHAMPAIGN 
 
 ETS STUDENT'S GUIDE 
 
 by 
 
 Al Davis 
 Jim Hart 
 Don Oxley 
 Keith Phillips 
 
 July 1972 
 
y 
 
 UIUCDCS-R -72-5^7 
 
 ETS STUDENT'S GUIDE 
 
 hy 
 
 Al Davis 
 Jim Hart 
 Don Oxley 
 Keith Phillips 
 
 July, 1972 
 
 Department of Computer Science 
 
 University of Illinois at Urb ana-Champaign 
 
 Urbana, Illinois 
 
 x This work was supported in part by the National Science Foundation under 
 Grant No. US NSF GJ-812. 
 
3 M 1 
 
 PS 
 
 Sfl- St 2- 
 
 TABLE OF CONTENTS 
 
 Page 
 
 1. INTRODUCTION 1 
 
 2. PUPETS 5 
 
 3 . EDETS 11 
 
 h . ASSETS 17 
 
 5. DEBETS 19 
 
 6. GIZMO 38 
 
ETS Student's Guide -1- July 1972 
 
 1. INTRODUCTION 
 
 1.1 What is ETS? 
 
 Educational Timesharing System, commonly called ETS, is a multi-user, 
 conversational timesharing system designed for use Toy students who are not 
 acquainted with the use of a computer. The basic system consists of a 
 monitor, a file system, an input/output system and a command string 
 interpreter. It runs on the PDP-11. 
 
 1.2 What is timesharing? 
 
 Timesharing is the property of an operating system that enables it 
 to give multiple users the illusion of being exclusive users. Under a 
 timesharing system a user can sit down at a console and in one or more 
 sessions write, debug, assemble, and run his program, all in an interactive 
 mode . 
 
 1.3 What facilities does ETS provide? 
 
 ETS keeps in its filing system, a number of useful systems programs 
 which may assist you in your programming. These include an editor (EDETS), 
 to add, delete, or alter segments of your source program; an assembler 
 (ASSETS), to assemble your source program written in PAL-11 into a machine 
 language module; a peripheral device handler (PUPETS), to enable you to 
 input or output your programs; and a complete debugging package (DEBETS) 
 for you to use in getting those nasty little bugs out of your code. 
 
 l.h How do you talk to ETS? 
 1A.1 Command Mode 
 
 Command Mode can be recognized by the presence of a period at the 
 11 Lnnin of the line on the teletype. This is the signal by the monitor 
 that he is ready to accept a command from you. 
 
ETS Student's Guide -2- July 1972 
 
 The folio-wing are valid commands: 
 
 1.4.1.1 .HEnm XXXXXX 
 
 This is the "hello" or login command which tells the monitor that 
 you want to be a user. You must login only if the monitor tells you to: 
 
 LOGIN PLEASE 
 In the above statement, n and m are code numbers and XXXXXX is a code word 
 which you must obtain from a T.A. or staff member. 
 
 1.4.1.2 ^SI n 
 
 This is the "size" command which asks the monitor to reserve for you 
 a certain amount of core. If you do not give the monitor this command, he 
 will automatically reserve IK (1024 words). In the above statement n is an 
 integer between and 5 inclusive. The units are IX words. 
 
 1.4.1.3 iME n 
 
 This is the "message" command which asks the monitor to print out 
 for you the error message designated by number n. It is not necessary for 
 you to use this command unless you receive an error message. 
 
 1.4.1.4 ^RU XXXXXX 
 
 This is the "RUN" command which requests the monitor to execute a 
 program located in the filing system. XXXXXX is the name of requested 
 program. For example, 
 
 ^RU ASSETS 
 vail start the execution of the assembler. This command, if successful, will 
 take you out of command mode, and put you into the hands of the executing 
 program. 
 
 1.4.1.5 j_BY 
 
 This is the "BYE" command which requests that the monitor cancel 
 your login command. That is, after this command, you will not be logged 
 in as a valid user of the system. 
 
ETS Student's Guide -3- July 1972 
 
 1.4.2 Other Modes 
 
 When not in command mode, you will probably be talking basically to 
 an individual systems program. Each of these has its own special character 
 which informs you of who you are talking to and what that program expects 
 from you. See the following sections of this manual for details of these 
 particular programs. 
 
 1.4.3 Special Characters 
 
 1.4.3.1 Carriage return [the key on the teletype marked "return"] is used 
 as a terminator or "break" character. That is, it is used at the end of 
 any input message from the teletype. For example, to ask the system to give 
 you a core size of 4K, you would type the characters 
 
 .81 4 
 and then type the "return" key to inform the system that you have completed 
 the message. 
 
 1.4.3.2 Line Feed is used as a terminator or "break" character also but 
 should only be used within certain systems programs when specifically 
 requested in this manual. 
 
 1.4.3 -3 Control B [push both the CNTL key and the B key simultaneously] can 
 be used to inhibit echo. If for example a program asks you for a code word 
 you should first hit Control B, then the code word, and then another Control 
 B to return to echo mode. This will simply suppress the printing of the code 
 word on the teletype paper. 
 
 1.4.3.4 Control V [push both the CNTL key and the V key simultaneously] 
 means cancel the present instruction. The particular uses of this will be 
 explained later within each systems program manual. 
 
ETS Student's Guide -4- July 1972 
 
 1.4.3.5 Control Q [push both the CNTL key and the 0, key simultaneously] 
 means "Quit this program." When Control Q is typed, the character string 
 tQUIT will he printed on the teletype, the present executing program will 
 
 be cancelled and you will be returned to command mode with the monitor again. 
 
 1.4.3.6 Control [push both the CNTL key and the key simultaneously] 
 means "Cancel the output." That is, if any program is printing a message 
 of any kind to you and you don't want to wait for it to complete, just type 
 Control and the printout will be cancelled. 
 
 1.4.3.7 Control U [push both the CNTL key and the U key simultaneously] 
 means "Cancel this input string." This should be used to cancel anything 
 you type on the teletype since your last carriage return or line feed. Thus 
 if you make many mistakes in typing a line, don' t type return. You should 
 type Control U and then start your line again. 
 
 1.4.3«8 Rubout on the teletype is equivalent to back space on a conventional 
 typewriter. To backspace n characters [i.e., cancel last n characters] 
 simply type rubout n times. Typing rubout will cause the teletype to retype 
 the characters that you are cancelling delimited by slashes. Thus if you 
 spell EDETS wrong by typing P instead of T and immediately rubout and then 
 type correctly, your teletype paper would look like: 
 
 ^RU EDEP\P\TS 
 The \P\ indicates that the P has been cancelled. 
 
ETS Student's Guide -5- July 1972 
 
 2. Peripheral Utility Package for ETS 
 
 2.1 PUPETS is a generalized file utility package "with which you can 
 manage your files. It is invoked by typing 
 
 RUN PUPETS 
 PUPETS will then identify itself and type a hash mark (#) to indicate 
 that it is ready to accept a command string. 
 
 2.2 A command string consists of up to six file strings. Separated by 
 commas. A file string consists of a file name and a switch list 
 separated by a slash. 
 
 2.2.1 A file name consists of three fields: 
 
 1. A device name 
 
 2. A file label 
 
 3. A project programmer number 
 
 2.2.1.1 The names of the devices are: 
 
 CDR Card Reader 
 
 LPT Line Printer 
 
 I'l'i; Paper Tape Reader 
 
 PTP Paper Tape Punch 
 
 DSK Disk 
 
 KBD User's Teletype 
 
 TTY Any Teletype 
 
 DTA DEC Tape 
 
 TTY and DTA require a device number after the name. TTYO is the same 
 
 as KBD. The device name is not necessary for disk files since disk 
 
 will be assumed if no device name appears. Device names are 
 
 terminated by a colon ( : ) . 
 
 2.2.1.2 The file label consists of up to six characters plus an 
 
 extension of up to three characters set off by a period. Characters 
 
 may be alphabetic, numeric, or the dollar sign. The file label is 
 
 optional for devices other than disk and DECtape. 
 
ETS Student's Guide -6- July 1972 
 
 2.2.1.3 The project programmer number is enclosed in square brackets 
 and consists of two numbers separated by a comma. If no project 
 programmer number appears, yours will be assumed. 
 2.2.1.4- The following are valid file names: 
 
 1. CDR: 
 
 2. TTY3: 
 
 3. PROGRM.BIN[15,3] 
 
 4. FILEA 
 
 2.2.2 A switch list consists of an arbitrary number of switch strings 
 
 separated by semi-colons (;). Switch strings consist of one switch followed 
 
 by parameters separated from each other and from the switch by colons (:). 
 
 2.2.2.1 The following are the switches presently defined: 
 
 OP Open the file. 
 
 CL Close the file. 
 
 RE Rename the file . 
 
 PR Change the protection on the file. 
 
 DE Delete the file from the UFD. 
 
 2.2.2.1.1 Open: If no parameters are present, it will give an error if the 
 file does not exist. The following parameters will cause the file to be 
 created: 
 
 CN Create if file does not exist. Otherwise, just open it. 
 
 EE Create if file does not exist. If file already exists, flag 
 an error. 
 
 2.2.2.1.2 Close: Close the file. 
 
 2.2.2.1.3 Rename: Parameter is the new name for the file and must be last 
 in the switch string. You must be the owner of the file to rename it. 
 
 2.2.2.1.4 Protect: Parameter is new protection code for the file. You 
 must be the owner of the file to change protection. 
 
ETS Student's Guide -7- July 1972 
 
 2.2.2.1.5 Delete: Remove the file from the UFD. You must be the owner 
 
 of the file to delete it. 
 
 2.2.2.2 If no switches are found, OP and CL will be assumed with no 
 
 parameters. 
 
 2.2.3 The following are examples of valid command strings: 
 
 1. FILEA/OP: CN; PR: 6; CL, CDR: 
 
 2. FILEB/RE: FILEC.EXT, FILED/DE 
 
 2.3 PUPETS may also be used to transfer data between files by typing a 
 transfer string between the object files (files into which data will be 
 transferred) and the source files (files from which data will be taken). 
 The transfer string is of the form 
 
 <mode : parameter < 
 "parameter" is an unsigned octal number less than 200000. 
 
 2.3.1 The mode indicates the nature of the data and how the parameter is 
 to be interpreted. 
 
 2.3.1.1 BI indicates that the data is binary, e.g., an assembled program. 
 Any parameter will be ignored. 
 
 2.3.1.2 LI indicates that the data is ASCII. The parameter indicates 
 the number of lines to be placed in each object file. 
 
 2.3.1.3 CH indicates that the data is ASCII. The parameter indicates 
 the number of characters to be placed in each object file. 
 
 2.3.2 Data is taken from the source files in order from left to right and 
 concatenated to form one data stream. Object files are filled in order 
 from left to right as indicated by the transfer string. 
 
 2.3.2.1 If no parameter is present or the parameter is zero, all of the 
 data will be transferred to the first object file. 
 
ETS Student's Guide -8- July 1972 
 
 2.3*2.2 If data remains to "be transferred after all object files have been 
 filled, the remainder is added to the last object file. 
 
 2.3 . 3 The following are examples of command strings: 
 
 a. FILEA, FILEB <LI:500<CDR: 
 
 This will place the first 500 lines in FILEA, and any remaining 
 lines in FILEB. If fewer than 500 cards are read, FILEB will not 
 be affected. 
 
 b. FILEC<CH:<PTR: 
 
 This will place all of the data on a paper tape, followed by the 
 data filed in FILEC. 
 
 c. FILEF, FILEG<BI:<PTR: 
 
 This will place all of the data on a paper tape in FILEF. FILEG 
 will not be affected. 
 
 2 A You may obtain information from your file directory by typing /DI any 
 place in the command string not within a file string. After executing all 
 switches in the command string, PUPETS will type the names of the files in 
 your file directory and their size in disk blocks in the order that they 
 were created. 
 
 2*5 It is necessary to be partially aware of what PUPETS will be doing 
 when you type a command string. 
 
 2.5.1.1 All files in the string will first be opened (whether or not the 
 open switch is present). Since no more than six files may be open at a 
 time, you should not leave too many files open from previous command 
 strings. 
 
 2.5.1.2 Files you asked to be renamed will then be renamed. 
 
 2.5.1.3 Any transfer specified will be performed. 
 
ETS Student's Guide -9- July 1972 
 
 2,5.lA Protection codes will be changed. 
 
 2.5.1.5 Files marked to be deleted will be removed. 
 
 2.5.1.6 Finally files with which the open switch was not present and/or 
 the close switch was present will be closed. 
 
 2.5.2 If at anypoint an error in protection, syntax, etc. is found, a message 
 will be typed and files will be returned to their state before the command 
 string was typed. 
 
 2.6 To exit from PUPETS type control Q, in response to a hash mark. 
 
 2.7 The current version of PUPETS has the following problems: 
 
 1. When transferring from one disk file to another in binary mode, 
 the object file will be one block longer than the source file. 
 Solution : None known at present. 
 
 2. If the protection code on a file is changed and then the user 
 tries to delete, rename, or write on the file, he may get a 
 protection violation message, particularly if the change in 
 protection was to remove some write protection. 
 
 Solution : After changing the protection code, log out then log back 
 
 in. 
 
 '). If the card reader runs out of cards before finding an end of 
 
 file card in LI or CH mode, the CR-LF on the last card is lost. 
 
 Solution : Be sure there is an end of file card at the end of your 
 
 deck, and keep cards in the hopper until the end if reached. 
 
 k. If an error occurs on the card reader (feed check, stacker fail, 
 
 timing, etc.) part or all of the card on which the error occurred 
 
 may be lost. 
 
ETS Student's Guide -10- July 1972 
 
 Solution : In BI mode, reread the deck. In LI or CH mode, keep 
 track of where the error occurred and correct it with EDETS. 
 5. DECtapes are not supported by PUPETS. 
 Solution: Use MAGETS. 
 
ETS Student's Guide -11- July 1972 
 
 3* Text Editor for the Edcuational 
 Timesharing System (EDETS) 
 
 EDETS is a text editor for use with the Educational Timesharing 
 System (ETS). It allows the user to display any text on the teletype, and 
 make corrections and improvements to it using simple one character commands. 
 
 3.1 Command Mode and Text Mode 
 
 There are two different modes of operation for EDETS: Command 
 Mode and Text Mode. In Command Mode the user is allowed to type in one of 
 22 possible commands for the editor to perform. While in Text Mode the 
 user may type in any text he wishes. He may not type in a command without 
 first entering Command Mode because EDETS will not recognize the command, 
 and instead it will treat it as text. To enter Command Mode from Text Mode 
 a line feed (LF) must be. typed. EDETS will respond by typing a # to signify 
 that it is in Command Mode. 
 
 Caution: The line feed will not be stored as part of the 
 text. However, a carriage return (CR) will cause EDETS 
 to include in the text a CR-LF sequence which designates the 
 end of line of text. Therefore it is important to type a 
 CR before entering Command Mode, or EDETS will append the 
 next line to the line just typed because there is no CR-LF 
 to designate the end of the line. Entering Text Mode is done 
 through various commands of EDETS. These commands require 
 text input and thus cause EDETS to go into Text Mode. 
 Example: # INSERT 
 
ETS Student's Guide -12- July 1972 
 
 This command tells EDETS to insert text. Thus EDETS goes into 
 Text Mode so that the text may be typed in. Note: The # was printed by 
 EDETS to signify it is in Command Mode. 
 
 3.2 Command Structure 
 
 3.2.1 The Character Location Counter (DOT) 
 
 Most EDETS commands are performed with respect to the movable 
 reference point, DOT. This pointer should be thought of as lying between 
 two successive characters. EDETS provides commands to move DOT so that 
 any character in text may be referenced. 
 
 3.2.2 Command Format 
 
 There are basically two different command formats. The first 
 type has no arguments and consists of just the command word. 
 
 Example: # BEGINNING 
 This will move DOT to the beginning of text. EDETS uses only the first 
 letter of command word to designate the command. Thus #B will result in 
 DOT being moved to the beginning of text too. 
 
 The second type requires some argument n. n may be any positive 
 
 15 
 or negative number from 1 to 327^7 (2 -l). If no sign precedes n it is 
 
 assumed positive. The command is of the form +n Command or Command +n. 
 
 Since EDETS uses only the first letter of the command the entire command 
 
 word need not be used. 
 
 Example: # ADVANCE 10 
 #A 10 
 
 # 10 ADVANCE 
 
 # 10 A 
 
 All four commands will move DOT to the beginning of the 10th line after the 
 current line that DOT is pointing to. 
 
ETS Student's Guide -13- July 1972 
 
 3.3 Commands 
 
 There are four basic groups of commands for EDETS: 
 
 (1) Commands for positioning DOT. 
 
 (2) Commands for inserting, deleting, and exchanging text 
 portions. 
 
 (3) Commands for searching for and manipulating strings of 
 characters. 
 
 (k) Commands for listing. 
 
 3.3*1 Commands for Positioning DOT 
 
 Advance - Advance DOT to the beginning of the nth line from 
 DOT. If n=0 DOT will he moved to the beginning of 
 the current line. 
 
 Beginning - Move DOT to the beginning of text. No argument 
 is used. 
 
 End - Move DOT to the end of text. No argument is used. 
 
 Go - Go to the previously marked location in text. No 
 argument is needed. This command is used in 
 conjunction with MARK. 
 
 Jump - Jump forward +n or backward -n characters. If 
 
 n=0 no action is needed. Caution: If jumping into 
 the next line remember that there is a CR-LF in 
 the text which must be jumped over. 
 
 Mark - Mark the current location of DOT in the text. 
 
 This command is used in conjunction with the GO 
 command. 
 
 3.3.2 Commands for Inserting, Deleting, and Exchanging Text Portions 
 
 Change - Delete +n characters starting at DOT and insert 
 in their place, text of arbitrary length. 
 
 Delete - Delete +n characters starting at DOT. If n=0 no 
 action is taken. 
 
 Insert - Insert text of an arbitrary length starting at DOT 
 until a line feed is typed to terminate text mode. 
 The line feed is not included as part of the text. 
 
ETS Student's Guide 
 
 -1k- 
 
 July 1972 
 
 Kill 
 
 - Kill +n lines starting with the current line. If 
 n=0 no action is taken. 
 
 Replace - Replace + lines starting with the current line 
 
 and insert in its place, text of arbitrary length. 
 
 3.5.3 Commands for Seeking and Manipulating Character Strings 
 
 Find - Find the +nth occurrence of a character string of 
 up to 72 characters starting at DOT. When typing 
 in the string to be searched for terminate it with 
 a LF. The LF is not included in the search 
 unless it was the only character typed. If the 
 LF is preceded by a CR the CR-LF sequence is 
 included in the search. If n=0, n=l is assumed. 
 
 Prefix - Prefix +n occurrences, starting at DOT, of Text 1 
 with Text 2*. The same rules apply for CR's and 
 LF's as are defined for FIND. 
 
 Suffix - Suffix +n occurrences, starting at DOT, of Text 1 
 with Text 2*. The same rules apply for CR's and 
 LF's as are defined for FIND. 
 
 Wipeout - Wipeout +n occurrences, starting at DOT. The 
 
 same rules apply for CR's and LF's as are defined 
 for FIND. 
 
 Xchange - Exchange +n occurrences, starting at DOT, of Text 1 
 with Text 2*. The same rules apply for CR's and 
 LF's as are defined for FIND. 
 
 ^Prefix, Suffix, and Xchange require two text strings. Neither can be more 
 than kO characters in length, but they need not be of equal length. Text 1 
 is typed first then Text 2. If either is longer than ^0 characters or a 
 control V is typed before the end of Text 2, no action will be taken. 
 
 3.3*^ Commands for Listing 
 
 Hole 
 List 
 
 - List the entire text. No argument is needed. 
 
 - List +n lines starting with the current line. If 
 n=0 no action is taken. 
 
 Number - List the current character position of DOT in 
 octal. No argument is necessary. 
 
 Type - Type +n characters beginning at DOT. If n=0 no 
 action is taken. 
 
 Verify - Verify the current line with an upward arrow showing 
 where DOT is . 
 
ETS Student's Guide -15- July 1972 
 
 3.3-5 Miscellaneous Commands 
 
 Control Q, - Quit editing. Puts the text in the disk file and 
 returns to monitor. 
 
 3.^- Operating Procedure 
 3-^.1 Invoking EDETS 
 
 To invoke EDETS simply type on the teletype RUN EDETS. 
 3 A. 2 Initial Dialogue 
 
 EDETS will identify itself and ask for the name of the file to 
 be edited. Your response should be: 
 
 (1) The name of a disc file of which you are the owner or a 
 file which has not been created. If the file already exists it 
 need not be open. If you do not wish to copy anything into the 
 file type a carriage return (CR) and EDETS will enter Command 
 Mode. 
 
 (2) If you wish to copy text into the file type a transfer mark 
 (<) following the file name and then type the name of either 
 another file or an input device. Example: To copy source from 
 the paper tape reader into a file name FILE type FILE<PTR: 
 After the copy is finished EDETS enters Command Mode. 
 
 3.^.3 Cautions when Copying 
 
 EDETS uses two successive form feeds to signify the end of the 
 file. Because of this caution must be taken when copying text into files. 
 3.^.3.1 Copying from Teletype 
 
 If there is a transfer mark and a teletype was specified as the 
 input device EDETS will assume that there is nothing in the disc file and 
 will enter Command Mode. 
 
ETS Student's Guide -l6- July 1972 
 
 3,1]-. 3. 2 Copying from the Card Reader 
 
 When copying from cards two form feeds will "be inserted after 
 the last card is read. 
 3.^.3 .3 Copying from the Paper Tape Reader 
 
 When copying paper tape two form feeds will he inserted if the 
 end of the tape is reached before two form feeds are found. Thus if no 
 form feeds exist on the tape the trailer tape will be inserted as part of 
 the text. These trailing characters should be deleted by you before doing 
 any editing. 
 J.k^J.k Copying from Another File 
 
 If a disk file is being copied and no form feeds are found before 
 the end of the file is reached EDETS will insert two form feeds and type 
 a warning message. This will probably mean there is some garbage at the 
 end of your file. This garbage should be deleted before continuing to edit, 
 
 3-5 Re s tr i ct i ons 
 3.5.1 File Size 
 
 EDETS cannot accept a file containing more than 32767 (2 -l) 
 characters. If the file is initially found to be larger than this, EDETS 
 will type a message and return to monitor mode. If during editing, an 
 insertion would cause the limit to be exceeded, a message is typed and the 
 insertion is not performed. 
 
 
 
ETS Student's Guide -IT- July 1972 
 
 k. ASSETS User's Guide 
 
 h. Description 
 
 ASSETS is a modified version of the PAL-11A assembler. Its input 
 is a disk file containing source statements and its output is an absolute 
 binary file. It presently has no provision for performing linkage editing. 
 
 ^-.1 Using Assets 
 
 ASSETS requires 5K of core in order to execute. It is initiated 
 by using the following command string when the system is in command mode. 
 
 .Size 5 
 
 .RUn ASSETS 
 
 (The lower case letters are optional, the periods are typed by 
 
 the system. ) 
 
 ASSETS will respond with: 
 
 SOURCE^ 
 In response, the user types from one to four file names separated by commas. 
 The files are assembled as if they were a single large file consisting of 
 the concatenation of the input files. ASSETS will check the validity of 
 the source files and if it is satisfied with them, it will respond 
 
 BINARY= 
 The user responds by typing a file name which may or may not exist. ASSETS 
 automatically adds an extension of the form BIN to the file name (e.g., FILEX 
 becomes FILEX.BIN). If this file exists, ASSETS will open it for output. 
 If it does not exist, it will create a file with that name and open it. 
 (Note that for files which do exist, ASSETS actually deletes and re-creates 
 them in case the new object listing is shorter than the old). ASSETS will 
 then type out 
 
ETS Student's Guide -18- July 1972 
 
 LISTING= 
 
 to which the user responds with a single character as follows: 
 
 N - produce no listing 
 
 E - list only statements containing errors and undefined 
 symbols on the teletype 
 
 T - produce a complete listing on the teletype 
 
 L - produce a complete listing on the line printer. 
 
 (if the line printer is currently being used, a message 
 
 will be printed saying that the line printer is unavailable 
 
 after which it will request another choice.) 
 
 If at any time during the assembly it is desired to terminate 
 
 the assembly, the user may type tQ, (CNTL key and Q) and ASSETS will terminate 
 
 as soon as it closes all files and releases the line printer if it is 
 
 being used. 
 
 k.2. Non-Standard Features 
 
 1. All registers (RO, Rl, ... SP, PC), carriage return (CR), and 
 line feed (LF) are already defined. 
 
 2. The assembly directive .NLIST may be used anywhere in the 
 source program to stop the generation of a listing at that point. 
 .LIST may be used to resume the listing if it is specified in 
 the LISTING command to ASSETS. 
 
 3. The directives .EJECT and .PAGE will cause the source listing 
 to continue on a new page. 
 
 k. If a .END statement is inadvertently left out, ASSETS will 
 supply one at the end of the last file. 
 
ETS Student's Guide -19- July 1972 
 
 5. DEBETS Command Manual 
 
 DEBETS is an interactive debugging package for student use with 
 ETS. Users can enter commands to load programs, execute them, and to 
 manipulate and examine their allotted core space at will. Like other ETS 
 programs (EDETS, PUPETS), DEBETS has a 'command mode' which is announced 
 by the typing of a special character (for DEBETS, a colon) and in which a 
 line of input containing commands is read, examined and executed. With a 
 few exceptions, DEBETS commands consist of a single character accompanied 
 by some numerical parameters, usually addresses. These parameters must 
 invariably be octal numbers, or an error is flagged and DEBETS returns to 
 command mode. Any addresses must be within the bounds allotted to the 
 user. (See section V.) As a rule, if a syntax error is made, DEBETS 
 types '?' and returns to command mode. (This is something of a hardship 
 on beginners, and will be changed. Space limitations at present make it 
 inadvisable to put in the extra code and message strings.) 
 
 The remainder of this manual describes the various commands. 
 Following is a short table of contents: 
 
 5.1 Opening, Examining and Changing Individual Locations 
 
 5-2 ASCII Insertion 
 
 5. 3 Dumping Core 
 
 5.k Disassemblies 
 
 5.5 Loading a Program - Changing Size 
 
 5.6 Setting Breakpoints, Executing a Program, Error Messages, I/O 
 Conventions 
 
ETS Student's Guide -20- July 1972 
 
 5.7 Special Routines: 
 
 Examining registers 
 
 Examining the breakpoint table 
 
 Dumping the instruction count 
 
 Dumping all registers 
 
 Opening the print register 
 
 Dumping the PC stack 
 
 Dumping the condition code, opening the status register 
 
 5.8 Dynamic Symbol Table 
 
 5.9 Storing and later Retrieveal of DEBETS Command Strings 
 5.10 Symbolic Program Patching — the Mini -Assembler 
 
 5.1 Opening, Examining and Changing Individual Locations 
 
 To examine a core location, type the address followed by a slash 
 ('/') to examine the word at that location, or a backslash ( f \ f ) to examine 
 the byte at that location. DEBETS prints the contents in the format 
 '=<value>', then returns to command mode without typing the standard colon. 
 The location is now 'open' and may be modified. The following inputs in 
 particular are of use while it is open: 
 
 5.1.1 Typing a line feed causes DEBETS to open and dump the next sequential 
 location. If an octal number was typed before the <LF>, this is inserted 
 into the word or byte presently open before the next is opened. 
 
 5.1.2 Typing <CR> causes DEBETS to insert any number typed into the 
 presently open location, 'close* it, and return to normal command mode with 
 a colon. 
 
 5.1.3 Typing 't ' (shift-N) causes DEBETS to insert any number typed into 
 the presently open location, and open the immediately preceding location. 
 (DEBETS decrements or adds 1 or 2 depending on whether the first location 
 opened is a byte or a word. ) 
 
ETS Student's Guide -21- July 1972 
 
 5.1.4 If a word is open, typing '©' causes DEBETS to take the ASCII 
 character following the quote mark and insert it into the presently open 
 location. If a word is open, the high byte becomes zero. This can be 
 used for changing individual bytes of a character string. 
 
 5.2 ASCII Insertion 
 
 DEBETS allows the user to change an entire character string at 
 will. Typing '<address>;A' causes DEBETS to input a new line from the 
 user to be placed in core starting at <address>. Every byte of the line 
 is placed in core except the terminal character of the line (CR, LF, or 
 ALTMODE). DEBETS then opens the byte immediately following the st ing in 
 core and awaits new commands. In this way the user can add, if he wishes, 
 some special terminal to the end of the string. 
 
 5.3 Dumping Core 
 
 Core may be dumped in three modes — word, byte, or ASCII. In 
 word mode, k words are dumped per line, in k 6-character strings followed 
 by the ASCII representation of those 8 bytes. In byte mode, 8 bytes are 
 dumped per line, in 8 3 -character strings, followed by the ASCII 
 representation (which is delimited by asterisks). In ASCII mode, l6 
 bytes are dumped in ASCII per line, with non-printing characters printed 
 as '.'. 
 
 A dump may be specified in one of two ways: 
 
 (1) By typing '<low address>; <high address>D' followed by 
 'W, 'B', or 'A' to indicate the mode, or 
 
 (2) By typing ' ;<low address>D' followed by 'W, 'B', or 'A' 
 followed by N dots ('.'), to produce N+l lines of output. 
 
ETS Student's Guide -22- July 1972 
 
 When the dump is complete, DEBETS returns to scanning the 
 original input string, so that multiple dump commands may be given in the 
 same line of input. 
 Examples : 
 
 '100;200DW *)' to dump words from 100 to 200. 
 '20;30DA^ ' to dump ASCII from 20 to 30. 
 ';1006DB. .. f ) ' to dump bytes in k- lines starting at 1006. 
 or several at once: 
 
 ' 100 ; 200DW 20 ; 30DA ; 1006DB . . . ^ * 
 
 5»b- Disassemblies 
 
 If the user wishes to check some instruction patches he has made, 
 he can do so by typing t <address>;D' . DEBETS then takes the word at 
 <address> (provided <address> is even), parses it, and prints a mnemonic 
 if it is a valid opcode, or else prints the message 'JIMK'. It then waits 
 for the user to type a line feed to disassemble the next instruction. If 
 line feed is not typed, DEBETS returns to command mode. 
 
 5.5 Loading a Program - Changing Size 
 
 5« 5*1 To load a program the user types 'KCK>', DEBETS responds by 
 first typing the size at which it is running (this is forced to 3 when DEBETS 
 starts executing). The user may alter the size by typing 3, k, or 5, or 
 type a terminal to bypass this and keep the same size. The size at which 
 DEBETS is running controls the amount of storage the user may access. At 
 size 3, the highest address he can reference is about 2000 (octal); at 
 size k, about 6000; at size 5> about 12000. (The user may quickly 
 ascertain his highest referenceable address by typing '.H<CB>' when in 
 normal command mode.) 
 
ETS Student's Guide -23- July 1972 
 
 5.5.2 Next DEBETS requests the name of a load file. If a terminal is 
 typed in response, DEBETS returns to command mode. Otherwise, DEBETS 
 inputs the name (which must be terminated by a <CB>, <LF>, or <ALTMODE>, 
 not a hundred blanks! ), and attempts to open the file. If it fails, a 
 message is typed and DEBETS again requests the file name. When it finally 
 gets a valid file open, it requests a load offset. Normally this will be 
 zero, but a nonzero offset causes the program to be loaded starting at 
 address <offset>. Thus, location 1000 in the assembler listing corresponds 
 to location 1000+<offset> of the user's area. This facility is useful 
 
 for testing relocatability of a program. 
 
 5.5.3 Finally, when the load file is open and the offset is determined or 
 it defaults to 0, DEBETS attempts to load the program. If an error occurs, 
 
 a message is typed, and DEBETS requests a load-file name again; otherwise, 
 
 DEBETS types 'LOADED O.K.', then requests a file name. 
 
 <N0TE: If the load file name has a .BIN extension, this must be included. > 
 
 5.6 Setting Breakpoints, Executing a Program, Error Messages, 
 I/O Conventions 
 
 5.6.1 Breakpoints 
 
 A 'breakpoint' is any (word) location specified as such by the 
 user. When the user's program is executing and it arrives at a breakpoint 
 location, a message of the form ! Bnnn:<address>'is typed and DEBETS returns 
 to command mode. The 'nnn' in the message is the number of the breakpoint, 
 of which there may be a maximum of 30 fi , numbered to 27q. The user may 
 create or delete breakpoints as follows: 
 
 Create: '<address>;B' to make <address> the first available 
 breakpoint in the breakpoint table. 
 
 Delete: ';B' to delete all breakpoints. 
 
 ' ;nB' to delete breakpoint number n. 
 
ETS Student's Guide -2k - July 1972 
 
 <NOTE: Multiple creates and deletes may be done in the same line of input. > 
 
 To be more specific: when the user starts his program executing, 
 all the locations he has specified as breakpoints are saved and replaced 
 by HALT instructions. Before DEBETS executes any instruction, it checks 
 to see if it is HALT. If it is, DEBETS checks to see if the HALT is at 
 the address of a breakpoint. If it is, DEBETS decrements a repeat count 
 for that breakpoint. If the count becomes zero, DEBETS types the message 
 'Bnnn:<address>', restores the original contents of all breakpoint locations, 
 and returns to command mode. (The repeat count is normally 1 — see section 
 VII on how to change it, under '.B'.) If the HALT is not at a breakpoint 
 address, DEBETS types 'BE :<address>', restores breakpoint locations, and 
 returns to command mode. (The 'BE' is for 'Bad Entry' or maybe 'Breakpoint 
 Error' . ) 
 
 5.6.2 Program Execution Commands 
 
 Program execution may be started in two possible ways. In 
 brief, the calling sequences are: 
 'P<print mode>' 
 
 or '<address>;<instruction limit>G<print mode>' . 
 5.6.2.1 The first is a 'Proceed' and is to be used mainly in conjunction with 
 breakpoints. DEBETS takes whatever address is in the user's program 
 counter, and attempts to start execution at that address. If it is the 
 address of a breakpoint, the breakpoint is ignored and the normal 
 instruction there is executed. After execution leaves this point, the 
 breakpoint is activated. THIS IS PECULIAR TO PROCEED, and is designed 
 for situations when execution has been stopped at a breakpoint, so that 
 it can PROCEED normally when a P-command is typed. The meaning of 
 <print mode> is explained below. 
 
 
ETS Student's Guide -25- July 1972 
 
 5.6.2.2 The G-command is used to start execution at the address 
 <address> typed by the user. Provided <address> is even and within bounds, 
 it is loaded into the user's program counter and execution begins. In 
 this case, if <address> is a breakpoint, there will be an immediate 
 breakpoint interruption and no instructions will have been executed. As 
 for the other parameters : 
 
 5.6.2.2.1 -^instruction limit> is the maximum number of instructions 
 DEBETS will execute before typing a message of some kind. If this number 
 is N, then, after executing N instructions, and assuming no breakpoints or 
 fatal errors occurred along the way, DEBETS types the address of the last 
 instruction executed, followed by a '?' to inquire if the user wants to 
 
 go on. At this point the user can type in an optional new <print mode>. 
 DEBETS then executes N more instructions. If instruction limit> is not 
 typed, it defaults to 100 (decimal). 
 
 5.6.2.2.2 <print mode> is any octal number. If it is present at all, 
 <instruction limit> is ignored (except in the special case when <print mode> 
 is a negative number — then DEBETS acts as if it weren't present, i.e., no 
 <print mode> and negative <print mode> are treated alike). The print mode 
 is used to control diagnostic output for each instruction executed. In 
 
 the present release of DEBETS, this is anything but fancy: If the print 
 mode is even, DEBETS prints the PC, opcode, and mnemonic for each 
 instruction. In either case, when the print is performed, DEBETS then 
 waits for a user response. The following alternative exist: 
 
 (a) If the first character typed is '/', DEBETS 
 continues executing the program in the same 
 manner. 
 
ETS Student's Guide -26- July 1972 
 
 (b) If a number is typed, DEBETS takes it for a new 
 print mode and continues executing the program. 
 
 (c) If <CR>, <LF> or <ALTM0DE> is typed, DEBETS 
 continues executing the program with no print for 
 each instruction, using whatever instruction 
 limit was last specified in a G~command, or the 
 default of 100 1Q . 
 
 (d) If control-V or control-Q, is typed, DEBETS returns 
 to command mode. 
 
 <NOTE: These rules apply also to typing a reply to the 
 instruction — limit interruption^ 
 
 5.6.2.3 Examples: 
 
 (1) ' 1000;G' start execution at 1000, with no special print 
 
 and an instruction limit of 100 . 
 
 (2) '2000;123J4-G' start execution at 2000, with no special print 
 
 and an instruction limit of 123^+n* 
 
 (3) '3000;G0' start execution at 3000 and print the PC for 
 
 each instruction executed. 
 (k) '3000;G1' start execution at 3000 and print the PC, opcode, 
 
 and mnemonic for each instruction executed. 
 (5) 'P0' resume execution with no change in the instruction 
 
 limit, and print the PC for each instruction. 
 <N0TE: The use of '/' to denote continuation allows the user, 
 when in print mode 0, to dump 8 or 9 PC ' s per line, by typing 
 1 /<A.LTM0DE> ' as a response. > 
 
 It is possible to completely remove the limit on number of instruction 
 executed — see under '.S/' in section VII. 
 
ETS Student's Guide -27- July 1972 
 
 5.6.3 I/O Conventions, Dynamic Core and Register Dumps 
 
 At present, DEBETS supports only teletype I/O for the user's 
 program. This is done as follows: 
 
 5.6.3.1 Input: EMT 0, followed by a buffer address. This causes DEBETS 
 
 to read a line from the user and store it in the 
 designated buffer. The terminal character (<CK>, <LE>, or 
 <ALTM0DE>) is counted as part of the input. (in 
 particular, if <CR> is the terminal, <LF> is tacked 
 on, too. ) 
 
 5. 6.3 . 2 Output: EMT 1, followed by a buffer to be typed, which must end 
 
 in a zero byte . No <.CR> or <LF> is added on; the user 
 must put these in himself if he wants them. The output 
 buffer may not exceed 200 characters. 
 
 (in point of fact, any even EMT causes input, and any odd EMT 
 
 causes output, with the exceptions below, but since DEBETS plans 
 
 using other EMT's for special purposes later, it's best to 
 
 restrict oneself to EMT and EMT 1.) 
 
 The user can get core dumps under program control by using one of 
 the following three special EMT's. In each case, the EMT must be followed 
 by 2 words giving the low and high addresses for the dump: 
 
 EMT 375 - dump in word mode 
 
 EMT 376 - dump in byte mode 
 
 EMT 377 - dump in ASCII mode 
 
 The user can selectively dump registers during program execution 
 by using the TBAP instruction. In this case, the low byte of the instruction 
 (the trap number) is scanned right-to-left, and registers corresponding to 
 1-bit s are dumped. For example, 
 
ETS Student's Guide -28- July 1972 
 
 TRAP 1 dumps RO 
 
 TRAP 200 dumps RT 
 
 TRAP 2^5 dumps RO, R2, R5, RT 
 
 TRAP 377 dumps all 8 registers. 
 
 TRAP is a special exception. When the user executes this, his 
 program is given control of the TRAP instruction, and may use it as described 
 in the PDP-11 handbook. Another TRAP returns TRAP to its register 
 dumping function. (Then another TRAP gives the user control of TRAP, 
 and so on. . . ) 
 
 5.6.4 Error Messages 
 
 As DEBETS executes a user program, it checks for a variety of 
 errors, such as addresses out of range or attempts to access words at odd 
 addresses. When DEBETS finds an error, it stops execution of the program, 
 prints out the PC, opcode and mnemonic for the instruction in error, plus 
 an explanatory error message, and returns to command mode. Following is 
 a list of possible error messages. The lack of continuity in the numbers 
 is the programmer's fault, not DEBETS' s. 
 #1: JUNK 
 
 The user tried to execute a non-opcode. 
 #2: RESERVED OP. 
 
 The user tried to execute WAIT, RESET, or RALT. 
 (Usually DEBETS does not actually execute HALT'S, since 
 they're used as breakpoint flags. However, if the user 
 does a proceed from a HALT, DEBETS attempts to execute it 
 and flags error #2 . ) 
 
 
ETS Student's Guide -29- July 1972 
 
 #3: ODD REG IN MODE 3- 
 
 In address mode 3, the register is supposed to contain 
 the address of a pointer, so this address must be even. 
 jfh. ODD PTR IN MODE 7. 
 
 In address mode 7> "the register contents are added to 
 an index word to get the address of a pointer. This address 
 must be even. 
 #5: ODD ADDR IN WORD OP. 
 
 The user tried to access a word at an odd address. 
 #6: ODD REG IN MODE 5. 
 
 This is similar to #3 — the register, after being 
 decremented, must contain the address of a pointer, so this 
 address must be even. 
 
 #8: ADDR TOO BIG. 
 
 The user tried to access out of his area. Because 
 DEBETS uses unsigned comparisons, an address of -1, say, 
 looks too big to it. 
 #10: BUFFER OUT OF RANGE. 
 
 On an I/O instruction, the buffer address following 
 the instruction was too large. 
 #11: 1"ST BYTE OF BUFFER=0. 
 
 On an output instruction, the trailer byte came a bit 
 too soon. 
 #12: BUFFER LENGTH >200. 
 
 DEBETS does not permit outputting more than 200 
 characters with one instruction. This is to protect against 
 the user's forgetting the trailer byte on the buffer and 
 then outputting some large chunk of his program. 
 
ETS Student's Guide -30- July 1972 
 
 #13: BAD PC. 
 
 The user executed an instruction which changed the PC 
 to something odd or out of bounds. This can happen if the 
 user is doing arithmetic on the PC, or if he executes 
 an interrupt and the interrupt vector contains a bad value 
 for the PC. 
 
 #1)+: BAD STACK PTR. 
 
 The user executed an instruction which uses the stack 
 pointer, and the latter was found to be odd or out of 
 bounds. For instance, JSR pushes one word onto the stack. 
 If the stack pointer is at the time, an error will result, 
 
 #15: STOP! 
 
 The user typed control-Q or control-V during the course 
 of program execution. This is the way to exit from 
 tediously long loops or just a way to get back to command 
 mode. The user should be careful using this, since, once 
 DEBETS is back in command mode, typing control-Q returns 
 the user to ETS. 
 #16: LO DUMP ADDR TOO BIG. 
 
 The user has requested a dump with EMT 375, 376 or 377, 
 and the low address is out of bounds. 
 #17: HI DUMP ADDR TOO BIG. 
 
 A dump was requested and the high limit was too large. 
 #18: LO DUMP ADDR NOT < HI ADDR. 
 
 The low address for a dump should be less than (or 
 equal) to the high address. 
 
ETS Student's Guide 
 
 -31- 
 
 July 1972 
 
 5.7.1 
 
 1 .<number>/' 
 
 
 ' .<number>\ ! 
 
 5.7.2 
 
 •.R' 
 
 5.7.3 
 
 '.N' 
 
 5.7 Special Routines 
 
 There are a number of special little routines --among them the 
 
 routines for opening register—which are called by typing '.' (dot) plus 
 
 some letter or number. These are described below under the calling string. 
 
 open register <number>; <humber> must be between 
 and 7. 
 
 dumps all registers, four to a line. 
 
 dumps the instruction count. Recall that DEBETS 
 counts the number of instructions the user 
 program executes. When the user returns to 
 command mode, this number can be dumped. Note, 
 however, that the instruction count is set to 
 by each P- or G- command, and that it is reset 
 before each instruction executed in a non-'null' 
 print mode and after an instruction limit 
 interruption. 
 
 dumps the "PC stack'. As the user program 
 executes, DEBETS keeps an 8-word stack containing 
 the most recent 8 values of the user's PC. The 
 1 .P' command dumps these 8-values, with the most 
 recent one first. 
 
 5.7.^ 
 
 .P' 
 
 5.7.5 '.C 
 
 5.7.6 '.c/' 
 
 5.7.7 '.S/' 
 
 dumps the current value of the user's condition 
 code in the format 'CVZN=nnnn' — in which, for 
 instance, the value of the C-bit is the first 
 or 1 to the right of the equal sign. 
 
 dumps the user's condition code as above, then 
 opens the user's program status register. 
 
 opens the 'print register'. This word is 
 normally non-zero. If the user alters it to 
 zero, he thereby disables the instruction limit 
 on executing his program. Then, when he gives 
 a P- or G- command, and provided he omits the 
 print mode (print mode is 'null'); DEBETS types 
 the message 'PRINT BOMBED. OKAY?'. If the user 
 responds with 'Y', DEBETS begins execution with 
 no limit on the number of instructions executed. 
 If DEBETS encounters no breakpoints, HALT'S, or 
 fatal errors, it will continue executing the user 
 program until the user types control-Q or control-V. 
 
ETS Student's Guide -32- July 1972 
 
 5.7.8 '.B/' causes DEBETS to type the numbers of the 
 
 breakpoints which are currently set. 
 
 5.7.9 '.B<n> , -where <n> is an octal number from to 27n, 
 
 starts an examination of the breakpoint table, 
 with breakpoint number n. If n is absent and 
 there is no slash after ' B T , the examination 
 begins with breakpoint 0. Whereever the 
 examination begins, DEBETS scans the table 
 until it finds a breakpoint that is set . Then 
 it dumps the breakpoint number and the address 
 of the breakpoint, in the format ' Bnnn=mmmmmm' . 
 Following this, it dumps the repeat count for 
 that breakpoint and waits to allow the user to 
 change it. Whether the user types a number or not, 
 if the user then types line feed, DEBETS continues 
 scanning the breakpoint table until it hits the 
 next breakpoint that is set, or, failing this, 
 returns to command mode. If the user does not 
 type line feed, DEBETS returns to command mode. 
 
 <N0TE: The sequence ' . B<n, ALTM0DE> ' allows 
 convenient changing of the repetition factor for 
 breakpoint $n on one line of print. > 
 
 5.7*10 ' .H T causes DEBETS to type the highest address currently 
 
 available to the user. 
 
 5.8 Dynamic Symbol Table 
 
 Ideally, a debugging package should allow its user to reference 
 core locations using the same symbols the user has defined in his assembly 
 listing. Unfortunately, this is at present not possible with DEBETS; the 
 problems of passing a symbol table from ASSETS to DEBETS, and the high 
 overhead involved in doing multiple disk accesses to get at symbols make 
 it infeasible for the time being. However, DEBETS does keep a small 
 table with space for (at present) ^0 1Q symbols. There are commands for 
 defining symbols, re-defining them, deleting them, and for clearing the 
 entire table. These commands are described below. The user-defined 
 symbols are used in the following ways: 
 5.8.1 Commands 
 
 5.8.1.1 If a breakpoint interrupt occurs at location <addr>, DEBETS 
 searches the symbol table for a symbol with value <addr>. If it finds 
 
ETS Student's Guide -33- July 1972 
 
 such a symbol it types the symbol as part of the breakpoint message. If, 
 for example, a breakpoint interrupt occurs at location 123^4- and symbol 
 XYZ has value 123^-, the message will look like 
 
 'BnrXYZ = 123 1 *-'. 
 
 If DEBETS finds no symbol with the required value, it merely dumps the 
 
 address, as already described. This feature makes identification of 
 
 breakpoints much easier. 
 
 5.8.1.2 When DEBETS dumps the 'PC stack' (see section 5-7, under '.P') 
 
 it dumps a symbol for each value of the PC if it finds a symbol with that 
 
 value. 
 
 5.8.1-3 When DEBETS dumps the address of an instruction in disassemblies, 
 
 it dumps a symbol if there is one whose value is the address. 
 
 5.8.1.U The mini -assembler (see section 5*10) allows symbolic referencing 
 
 in an instruction patch. . 
 
 Commands to the symbol table handler consist of the letter 'S' 
 followed by a series of 'fields' specifying operations to be performed. 
 These fields may be optionally separated by slashes ('/'). The slashes 
 are used for error recovery: if a field looks bad or unintelligible to 
 DEBETS, it scans the input until it finds a slash, then resumes processing 
 of fields. The following are the formats of valid fields: 
 5.8.2 Field Formats 
 
 5.8.2.1 Symbol definition: 
 
 <symbol>=<value> defines a symbol with a given 
 
 value, e.g., ABC = 12^56. 
 
 <symbol>=!<value> defines a symbol with a given 
 
 value; if the symbol has already 
 been defined, it is to be re-defined. 
 E.g«, if A has already been defined 
 to have value 111, then A = !222 
 redefines it to have value 222. 
 Just A = 222 results in an error 
 message telling that A is already 
 defined. 
 
ETS Student's Guide 
 
 -■5k- 
 
 July 1972 
 
 <symbol>=<value>;nB 
 or <symbol>=!<value>;hB 
 
 defines a symbol with a given value, 
 then sets a breakpoint at address 
 <value>. E.g., A = 1000 ;B defines 
 A to have value 1000, then sets the 
 location 1000. Similarly, A = 1000; 2B 
 defines A to have value 1000, then 
 sets breakpoint 2 at 1000. 
 
 <Note: Symbols must obey standard PAL convention, 
 
 i.e. 
 
 must 
 
 consist of characters A-Z, 0-9, '$', and 
 
 and must begin 
 
 with A-Z, '$', or 
 are truncated. > 
 
 5.8.2.2 Symbol deletion: 
 
 -<symbol> 
 
 Symbols longer than 6 characters 
 
 deletes <symbol> from the table. 
 E.g., -XYZ deletes XYZ. These may 
 be strung together, e.g., -A-B-FGH-J 
 to delete A,B,FGH, and J. 
 
 -<symbol>;B 
 
 5.8.2.3 
 
 5.8.2A 
 5.8.2.5 
 
 ?<value> 
 
 < 
 
 deltes <symbol> from the symbol 
 table. If a breakpoint is set at 
 location <value of symbol>, it is 
 deleted. E.g., if A = 1000 and 
 a breakpoint is set at 1000, then 
 ' S-A;B' deletes the symbol A and 
 the breakpoint at 1000. 
 
 deletes all symbols from the table. 
 
 types out all symbols with a given 
 value . 
 
 dumps all the symbols presently defined. 
 
 returns DEBETS to normal scanning 
 immediately following '<' . For 
 instance, suppose in one command 
 a symbol and breakpoint are defined: 
 A = 1000 ;2B. Later, the user decides 
 to get rid of A and the breakpoint. 
 He can do so with 'S-A<;2B' . This 
 deletes A, returns to normal 
 scanning, then deletes breakpoint 
 2. This may of course also be done 
 with 'S-A;B'. 
 
ETS Student's Guide -35- July 1972 
 
 5.9 Storing and Later Retrieval of DEBETS Command Strings 
 
 The commands typed to DEBETS are received as strings of ASCII 
 characters which DEBETS scans for certain characters which represent 
 operations to be performed. It is possible for DEBETS to get such a 
 string from anywhere in core. In particular, the user can place an 
 ASCII string somewhere in his area, then tell DEBETS to use it as the 
 next command string. There are three ways to do this: 
 
 5.9.1 In tells DEBETS to find its next 
 
 command string at breakpoint n. 
 E.g., if breakpoint 20 is set at 
 123k, 120 causes DEBETS to process 
 the string at 123^ • 
 
 5.9.2 F<symbol> causes DEBETS to process the string 
 
 at address <value of symbol>. 
 E.g., 'FLOP' causes DEBETS to look 
 up 'LOP' in the symbol table. If 
 it doesn't find 'LOP', it flags an 
 error. Otherwise, if, say, 'LOP' = 
 123^, DEBETS processes the command 
 string at user location 123^ • 
 
 5«9«3 F<address> causes DEBETS to process the string 
 
 at <address^, e.g., F123^ causes it 
 to process the string at user location 
 
 <Note: If DEBETS is processing a command string from user 
 area and encounters an 'I 1 or 'F' command, it flags an 
 error and returns to normal command mode.> 
 
 5.10 Symbolic Program Patching — the Mini -Assembler 
 
 If the user wishes to insert an instruction in a certain 
 location, he can do so by typing l <address>:<instr>* . DEBETS then 
 assembles the instruction, inserts it at <address> (provided <address> 
 is even), and prints out the location following the last word inserted 
 followed by a colon. 
 
 The instruction to be assembled may be virtually any valid 
 instruction or a single symbol. The user should use registers R6 and 
 R7, not the symbols SP and PC. DEBETS will consider SP and PC as user 
 defined symbols. If the instruction contains a symbol that is not in 
 
ETS Student's Guide -%- July 1972 
 
 the dynamic symbol table, it will print out the undefined symbol, 
 followed by a question mark. The user may then define the symbol by 
 typing its value, followed by a <CE>. The user may return to command 
 mode by typing a <CR> without giving any value. 
 
 DEBETS checks for a variety of errors, such as addresses out 
 of range or attempts to assemble instructions at odd locations. Usually 
 when an error is detected, an error message is printed, and DEBETS prints 
 out the original location number (if valid), followed by a colon, so 
 the user may enter the corrected instruction. Following is a list of 
 possible error messages. 
 
 #1: ATTEMPT TO ASSEMBLE AT ODD LOCATION 
 
 The location given was odd. DEBETS increments it 
 and prints it followed by a colon, so the instruction 
 may be reinserted. 
 fd: ADDR TOO BIG 
 
 The location given was outside the user's area. 
 DEBETS returns to command mode. 
 
 For the following errors, DEBETS prints the error message and 
 allows the user to insert a corrected instruction in the original location. 
 #3: BRANCH OFFSET SIZE ERROR 
 
 The location to be branched to is out of range of 
 the branch instruction. 
 #<■: TOO MANY OPERANDS 
 
 The user has typed an instruction with more than 
 two operands. 
 
ETS Student's Guide -37- July 1972 
 
 #5: INVALID OPERAND 
 
 This includes errors in usage such as RTS @7fLABEL 
 as well as syntactical errors like TST -(R^)+. 
 #6: INVALID MNEMONIC 
 
 The mnemonic given was invalid. Symbols to be 
 inserted have no operands, e.g., 1020: SYMBOL is a 
 valid insertion, whereas 1020: SYMBOL <operand> will 
 flag error #6. 
 
ETS Student's Guide -38- July 1972 
 
 6 . GIZMO 
 
 GIZMO was designed to aid CS 201 students in learning basic assembly 
 language concepts. It is very easy to use. 
 
 6.1 GIZMO is invoked by typing 
 
 RIM STUD 
 "when in monitor command mode. GIZMO will then ask you to identify yourself. 
 Please type your name followed by a return. GIZMO will then ask for a 
 lesson name. Please type the name of the lesson that your T.A. has indicated. 
 
 6.2 GIZMO will ask you a series of questions. Answer each one and terminate 
 each response with a carriage return. If you're correct, GIZMO will 
 usually say "very good." Otherwise, it will attempt to give you some helpful 
 hints. If you are sure your answer is correct, and GIZMO says you're not, 
 please call your T.A. for assistance. 
 
 6.3 If you have no idea what the correct answer is, you may ask for help 
 hy typing HELP. If you want to give up, type GIVE-UP. 
 
 6.1+ The lesson has been completed when GIZMO asks you to identify yourself 
 again . 
 
IBLIOGRAPHIC DATA 
 <EET 
 
 Title and Subtitle 
 
 1, Report No, 
 
 UIUCDS-R-72-5^7 
 
 3. Recipient's Accession No. 
 
 5. Report Date 
 
 July, 1972 
 
 ETS Student's Guide 
 
 Author(s) 
 
 Al Davis, Jim Hart, Don Oxley, Keith Phillips 
 
 8. Performing Organization Rept. 
 No. 
 
 ' Performing Organization Name and Address 
 
 Department of Computer Science 
 University of Illinois 
 Urbana, Illinois 6l801 
 
 10. Project/Task/Work Unit No. 
 
 11. Contract /Grant No. 
 
 GJ-812 
 
 Sponsoring Organization Name and Address 
 
 National Science Foundation 
 Washington, D. C. 
 
 13. Type of Report & Period 
 Covered 
 
 Research 
 
 14. 
 
 Supplementary Notes 
 
 Abstracts 
 
 This manual is intended to serve as a reference to persons 
 who wish to use any of the systems programs in the permanent library 
 of the Educational Timesharing System - ETS. It discusses the basic 
 commands used to communicate with the monitor, the editor (EDETS), 
 the interpreter (DEBETS), the assembler (ASSETS), and the CAI system 
 (GIZMO). 
 
 1 Key Words and Document Analysis. 17o. Descriptors 
 
 1 • ldentitiers/Open-F.nded Terms 
 
 ll COSAT! Field/Group 
 
 11 Av. .liability Statement 
 
 f* M N TIS-19 (10-70) 
 
 19. Security Class (This 
 Report) 
 
 UMQLASS1E1EB, 
 
 i m^ 
 
 20. Security Class (This 
 
 Page 
 UNCLASSIFIED 
 
 21. No. of Pages 
 
 58 
 
 22. Price 
 
 USCOMM-DC 40329-P71 
 
imv 
 
 
OCv 
 
 Z* 
 
 \973