Return to 1401 Software DevelopmentYou may note that most of the document is directly from Bob Supnik's document. Supplemented I1401 User Manual
Written to include and supplement i1401_doc_version33-0.html by Bob Supnik
I intend to make additions in italics.
(Alpha release) If/when you find a bug in this presentation, please e-mail Ed Thelen with problem (and possible solution).Table of Contents
- 0.1 Getting started
- 0.2 Try a one line (one card) program - HELLO WORLD
- 0.3 Result of typing H{elp} into SIMH 1401 Simulator
- 1. Build Files - not included in this supplement -
- 2. Device Names used in command line
- 2. Simulator Stop Conditions
- 2.1 CPU Options
- 2.1 Memory bits
- 2.1 CPU registers
- 2.1 CPU instruction history
- 2.2 1402 Card Reader/Punch (CDR, CDP, STKR)
- 2.3 1403 Line Printer (LPT)
- 2.4 1407 Inquiry Terminal (INQ)
- 2.5 1311 Disk Pack (DP)
- 2.6 729 Magnetic Tape (MT)
- 2.7 Symbolic Display and Input
- 2.7 Character Sets
0.1 Getting started
- This write up assumes that you are running a Microsoft Windows machine and can get into a command line prompt (DOS) window. Usually clicking on START, then ACCESSORIES then COMMAND PROMPT will do it.
- Make a directory/folder where you will do your Simulation work - I will use as an example SIMHV
- Download the current version into your example SIMHV directory from http://simh.trailing-edge.com/ clicking on the link "Windows executables".
- I the directory you will find a .zip file, named something like simhv33-1-exe.zip Double click on this file to "unzip" this file. If your system does not have a program to handle .zip files, go to http://www.winzip.com/ and either
- buy and download the $29 program
- or download the evaluation version
and install it. If you just installed the program, you may have to click on the .zip file again to get the unzip program running.- The unzip program shows a number of files, click on i1401.exe to highlight it and click "extract"
You will be asked what directory to unzip the file to. Select your SIMHV directory, and click "extract" button check to see that a file i1401.exe is in your SIMHV directory.
- Double click on the i1401.exe icon in your SIMHV directory. This should cause a window with a black background to pop up. In white letters you should see something like
- IBM 1401 simulator V3.3-1
- sim>
- Double click to the right of the "sim>" and a blinking cursor should appear
- Type "show version" followed by an enter, and version information should be typed out. and example is
sim> show version
IBM 1401 simulator V3.3-1 [32b data, 32b addresses, no Ethernet]
sim>- Type "help" followed by an enter, and a lengthy help should appear on the black background. It should resemble the help display in this web page. (There can be differences from version to version. V3.3-0 supported a debug file not supported in V3.3-1)
0.2 Try a one line (one card) program - HELLO WORLD
- OK - the simulator seems to function in your machine.
Now lets try a sample program, next line down, and see what happens.
,008015,022029,036043,050054,055062,063065,066077/333/M0762502F1.HELLO WORLD 0 1 2 3 4 5 6 7 8 12345678901234567890123456789012345678901234567890123456789012345678901234567890The line above is an actual one card program that prints to the printer (actually in this simulator it "prints" to a file).Copy the line above to Windows NOTEPAD, assuring that the first comma on the left is actually in column 1. Place an enter or carriage return after the last character in the line.
Save the contents of NOTEPAD to the file PROG.TXT in your SIMHV directory.
You now have three files in your SIMHV directory, the simhv.zip file, and i1401.exe and PROG.TXT Enter the following commands at the sim> cursor
at cdr PROG.TXT at lpt HELLO.TXT b cdr
you should get a message
HALT instruction, IS: 66 (DCW @HELLO WORLD@)
(NOTE: The output "HELLO WORLD" is written to the file HELLO.TXT when the simulator halts.)Before you exit the simulator, enter e -n 1:80
the actual instructions in memory, from the card, are displayed.Then enter e -d 1:80
and see the input program and the word marks as 1s under each character in memory with a word mark.Now exit the simulator by entering exit
Note that the black DOS window disappears (and the text is moved into the output file).In your WINDOWS EXPLORER window, double click on the new file HELLO.TXT and notice the HELLO WORLD message.
0.3 Result of entering H{elp} into SIMH 1401 Simulator
r{eset} {ALL|<device>} reset simulator e{xamine} <list> examine memory or registers - Van Snyder says - To examine locations a-b as machine code, use e -m a-b or e -m a:b This will dump length-3 fields as DSA (i.e., machine address converted to decimal), and any other invalid-length or invalid-opcode field as DCW.
To dump in BCD with word marks, looking somewhat like the kind of dump one used to get from the IBM customer-contributed library dump, or the equivalent German one, i.e., with word marks represented by "1" on the next line, use
e -d a-b or e -d a:b ie{xamine} <list> interactive examine memory or registers d{eposit} <list> <val> deposit in memory or registers id{eposit} <list> deposit in memory or registers ev{aluate} <expr> evaluate symbolic expression ru{n} {new PC} reset and start simulation go {new PC} start simulation s{tep} {n} simulate n instructions c{ont} continue simulation b{oot} <unit> bootstrap unit br{eak} <list> set breakpoints nobr{eak} <list> clear breakpoints at{tach} <unit> <file> attach file to simulated unit det{ach} <unit> detach file from simulated unit as{sign} <device> <name> assign logical name for device dea{ssign} <device> deassign logical name for device sa{ve} <file> save simulator to file rest{ore}|ge{t} <file> restore simulator from file l{oad} <file> {<args>} load binary file du{mp} <file> {<args>} dump binary file exi{t}|q{uit}|by{e} exit from simulation set console arg{,arg...} set console options set <dev> OCT|DEC|HEX set device display radix set <dev> ENABLED enable device set <dev> DISABLED disable device set <dev> DEBUG={arg} set device debug flags set <dev> NODEBUG={arg} clear device debug flags set <dev> arg{,arg...} set device parameters set <unit> ENABLED enable unit set <unit> DISABLED disable unit set <unit> arg{,arg...} set unit parameters sh{ow} br{eak} <list> show breakpoints on address list sh{ow} con{figuration} show configuration sh{ow} cons{ole} {arg} show console options sh{ow} dev{ices} show devices sh{ow} m{odifiers} show modifiers sh{ow} n{ames} show logical names sh{ow} q{ueue} show event queue sh{ow} ti{me} show simulated time sh{ow} ve{rsion} show simulator version sh{ow} <dev> RADIX show device display radix sh{ow} <dev> DEBUG show device debug flags sh{ow} <dev> MODIFIERS show device modifiers sh{ow} <dev> NAMES show device logical name sh{ow} <dev> {arg,arg...} show device parameters sh{ow} <unit> {arg,arg...} show unit parameters do <file> {arg,arg...} process command file echo <string> display h{elp} type this message h{elp} <command> type help for command ! execute local command interpreter ! <command> execute local host command 2.) Device Names used in command line
CPU IBM 1401 CPU with 16K of memory CDR,CDP IBM 1402 card reader/punch LPT IBM 1403 line printer INQ IBM 1407 inquiry terminal DP IBM 1311 disk pack with five drives MT IBM 729 7-track magnetic tape controller with six drives 2.) Simulator Stop Conditions
(Sorted) The IBM 1401 simulator implements many unique stop conditions. On almost any kind of error the simulator stops:
address register wrap-around card reader hopper empty hanging $ in MCE with EPE enabled I/O check with I/O stop switch set invalid A address invalid B address invalid branch address invalid disk address compare invalid disk drive invalid disk sector address invalid disk sector count invalid instruction length invalid magtape record length invalid magtape unit number invalid modifier character no word mark under opcode reference to non-existent device reference to non-existent memory single character A field in MCE single character B field in MCE skip to unpunched carriage control tape channel unimplemented opcode write to locked magtape drive 2.1 CPU-Options
The CPU options include a number of special features and the size of main memory. Note that the Modify Address special feature is always included when memory size is greater than 4K. Initially, memory size is 16K, and all special features are enabled.
SET CPU XSA enable advanced programming special feature SET CPU NOXSA disable advanced programming SET CPU HLE enable high/low/equal special feature SET CPU NOHLE disable high/low/equal SET CPU BBE enable branch on bit equal special feature SET CPU NOBBE disable branch on bit equal SET CPU MR enable move record special feature SET CPU NOMR disable move record SET CPU EPE enable extended print edit special feature SET CPU NOEPE disable extended print edit SET CPU MDV enable multiply/divide special feature SET CPU NOMDV disable multiply/divide SET CPU 4K set memory size = 4K SET CPU 8K set memory size = 8K SET CPU 12K set memory size = 12K If memory size is being reduced, and the memory being truncated contains non-zero data, the simulator asks for confirmation. Data in the truncated portion of memory is lost. SET CPU 16K set memory size = 16K 2.1 Memory bits
For more information on octal values, see
1401CardCode1-sorted.html 2.1) CPU registers
CPU registers include the visible state of the processor. The 1401 has no interrupt system.
name size comments IS 14 instruction storage address register (PC) AS 14 A storage address register BS 14 B storage address register ASERR 1 AS invalid flag BSERR 1 BS invalid flag SSA 1 sense switch A SSB 1 sense switch B SSC 1 sense switch C SSD 1 sense switch D SSE 1 sense switch E SSF 1 sense switch F SSG 1 sense switch G EQU 1 equal compare indicator UNEQ 1 unequal compare indicator HIGH 1 high compare indicator LOW 1 low compare indicator OVF 1 overflow indicator IOCHK 1 I/O check switch PRCHK 1 process check switch ISQ[0:63] 14 IS prior to last branch; most recent IS change first WRU 8 interrupt character 2.1 CPU instruction history
The CPU can maintain a history of the most recently executed instructions. The maximum length for the history is 65536 entries. This is controlled by the SET CPU HISTORY and SHOW CPU HISTORY commands:
SET CPU HISTORY clear history buffer SET CPU HISTORY=0 disable history SET CPU HISTORY=n enable history, length = n SHOW CPU HISTORY print CPU history SHOW CPU HISTORY=n print first n entries of CPU history 2.2 1402 Card Reader/Punch (CDR, CDP, STKR)
The IBM 1402 card/reader punch is simulated as three independent devices: the card reader (CDR), the card punch (CDP), and the reader and punch stackers (STKR). STRK units 0, 1, 2, and 4 correspond to the reader normal stacker, reader stacker 1, shared stacker 2/8, and punch stacker 4, respectively. The card reader supports the BOOT command. BOOT CDR reads a card image into locations 1-80, sets a word mark under location 1, clears storage, and then transfers control to location 1.
The card reader reads data from disk files, while the punch and stackers write data to disk files. Cards are simulated as ASCII text lines with terminating newlines; column binary is not supported. For each unit, the POS register specifies the number of the next data item to be read or written. Thus, by changing POS, the user can backspace or advance these devices.
The card reader registers are:
name size comments LAST 1 last card indicator ERR 1 error indicator S1 1 stacker 1 select flag S2 1 stacker 2 select flag POS 32 position TIME 24 delay window for stacker select BUF[0:79] 8 reader buffer The card punch registers are:
name size comments ERR 1 error indicator S4 1 stacker 4 select flag S8 1 stacker 8 select flag The stacker registers are:
name size comments POS0 32 position, normal reader stack POS1 32 position, reader stacker 1 POS2 32 position, shared stacker 2/8 POS4 32 position, punch stacker 4 Error handling is as follows:
device error processed as reader end of file if SSA set, set LAST indicator on next Read, report error and stop reader,punch not attached report error and stop . OS I/O error print error message
if IOCHK set, report error and stopotherwise, set ERR indicator stacker not attached ignored . OS I/O error print error message
if IOCHK set, report error and stop2.3 1403 Line Printer (LPT)
The IBM 1403 line printer (LPT) writes its data, converted to ASCII, to a disk file.
The line printer supports three different print character sets or "chains": In addition, the line printer can be programmed with a carriage control tape. The LOAD command loads a new carriage control tape:
command character set or chain SET LPT PCF full 64 character chain SET LPT PCA 48 character business chain SET LPT PCH 48 character FORTRAN chain The DUMP command is not implemented.
LOAD load carriage control tape file The format of a carriage control tape consists of multiple lines. Each line contains an optional repeat count, enclosed in parentheses, optionally followed by a series of column numbers separated by commas. Column numbers must be between 1 and 12; a column number of zero denotes top of form. The following are all legal carriage control specifications:
The default form is 66 lines long, with column 1 and the top of form mark on line 1, and the rest blank.
no punch (5) 5 lines with no punches 1,5,7,8 columns 1, 5, 7, 8 punched (10)2 10 lines with column 2 punched 1,0 column 1 punched; top of form The line printer registers are:
name size comments LINES 8 number of newlines after next print LFLAG 1 carriage control flag (1 = skip, 0 = space) CCTP 8 carriage control tape pointer CCTL 8 carriage control tape length (read only) ERR 1 error indicator POS 32 position CCT[0:131] 32 carriage control tape array Error handling is as follows:
error processed as not attached report error and stop OS I/O error print error message
if IOCHK set, report error and stopotherwise, set ERR indicator
2.4 1407 Inquiry Terminal (INQ)
The IBM 1407 inquiry terminal (INQ) is a half-duplex console. It polls the console keyboard periodically for inquiry requests. The inquiry terminal registers are:
name size comments INQC 7 inquiry request character (initially ESC) INR 1 inquiry request indicator INC 1 inquiry cleared indicator TIME 24 polling interval When the 1401 CPU requests input from the keyboard, the message [Enter] is printed out, followed by a new line. The CPU hangs waiting for input until either the return/enter key is pressed, or the inquiry request character is typed in. The latter cancels the type-in and sets INC.
The inquiry terminal has no errors.
2.5 1311 Disk Pack (DP)
The disk pack controller supports 5 drives, numbered 0 through 4. Disk pack options include the ability to enable address writing (formatting).
SET DPn ADDROFF set unit n address enable off SET DPn ADDRON set unit n address enable on Units can also be set ENABLED or DISABLED.
Unlike most simulated disks, the 1311 includes explicit representation for sector addresses. This is to support non-standard formats, such as the inclusion of the drive number in the sector address. As a result, 1311 sectors are 106 characters long: 6 address characters and 100 data characters. If the 1311 has not been formatted, the addresses are blanks and are synthesized, if needed, based on the sector number.
The 1311 also supports two modes of operation: move mode and load mode. In move mode, word marks are ignored on writes and left untouched on reads, and sectors hold 100 characters. In load mode, word marks are included on writes and stored on reads, and sectors hold 90 characters. No attempt is made to deal with sectors written in load mode and read in move mode, or vice versa; on a real 1401, this causes a fatal parity error.
The disk pack controller implements these registers:
name size comments ACC 1 access error indicator PWC 1 parity or write check error indicator WLR 1 wrong length record error indicator UNA 1 unequal address compare error indicator DSK 1 any disk error indicator BSY 1 disk access busy indicator LASTF 3 most recent function TIME 24 seek time The 1311 has a primitive overlapped seek capability. If TIME is set non-zero, the 1311 will report itself busy for the specified amount of time following a seek. This allows programs to utilize the seek time for processing.
Error handling is as follows:
error processed as not attached set DSK indicator
if IOCHK set, report error and stop1311 data files are buffered in memory; therefore, end of file and OS I/O errors cannot occur.
2.6 729 Magnetic Tape (MT)
The magnetic tape controller supports six drives, numbered 1 through 6. Magnetic tape options include the ability to make units write enabled or write locked.
SET MTn LOCKED set unit n write locked SET MTn WRITEENABLED set unit n write enabled Units can also be set ENABLED or DISABLED. The magnetic tape simulator supports the BOOT command. BOOT MT reads the first record off tape, starting at location 1, and then branches to it.
The magnetic tape controller implements these registers:
name size comments END 1 end of file indicator ERR 1 error indicator PAR 1 parity error indicator POS1..6 32 position, drives 1..6 Error handling is as follows:
error processed as not attached report error and stop end of file set error indicator OS I/O error print error message
set error indicator
if IOCHK set, report error and stop
2.7 Symbolic Display and Input
The IBM 1401 simulator implements symbolic display and input. Display is controlled by command line switches:
-c display as single character (BCD for CPU and MT, ASCII for others) -s display as wordmark terminated BCD string (CPU only) -m display instruction mnemonics (CPU only) -d display 50 characters per line, with word marks denoted by "1" on the line below In a CPU character display, word marks are denoted by ~.
Input parsing is controlled by the first character typed in or by command line switches:
' or " or -c or -s characters (BCD for CPU and MT, ASCII for others) alphabetic instruction mnemonic numeric octal number Instruction input is free format, with spaces separating fields. There are six instruction formats: 1, 2, 4, 5, 7, and 8 characters:
1 character opcode 2 character opcode 'modifier 4 character opcode address 5 character opcode address 'modifier 7 character opcode address address 8 character opcode address address 'modifier Addresses are always decimal, except for special I/O addresses in the A field, which may be specified as %xy, where x denotes the device and y the unit number.
For the CPU, string input may encompass multiple characters. A word mark is denoted by ~ and must precede the character to be marked. All other devices can only accept single character input, without word marks.