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Language Assembler (EDSAC)

Date:04/20/05
Author:Anonymous
URL:n/a
Comments:0
Info:n/a
Score:No votes yet 
As you may well know, the EDSAC was the world's first stored-program
computer. Correspondingly, its assembly language is one of the most 
basic and obscure programming languages known to man, and is unbelievably
difficult to program in.

In the absence of access to the original EDSIC (long since dismantled), an
EDSAC simulator, on which my program may be run, can be downloaded from
http://www.dcs.warwick.ac.uk/~edsac/


[----------------------------------------]
[-           by James Lingard           -]
[-             January 2004             -]
[-                                      -]
[-        http://www.jchl.co.uk/        -]
[----------------------------------------]
[- Download an EDSAC simulator from     -]
[- http://www.dcs.warwick.ac.uk/~edsac/ -]
[-                                      -]
[- This program uses Initial Orders 2.  -]
[----------------------------------------]


[----------------------------------------]
[-           Code letter data           -]
[----------------------------------------]
T 44 K   [start loading at address 44]

P 128 F  [code letter ! - base address of printing subroutine]
P 192 F  [code letter H - base address of string printing subroutine]

P 320 F  [code letter N - base address of string 1]
P 384 F  [code letter M - base address of string 2]
P 448 F  [code letter & - base address of string 3]
P 512 F  [code letter L - base address of string 4]

P 256 F  [code letter X - base address of the constant data area]
P 288 F  [code letter G - base address of the variable data area]


[----------------------------------------]
[-             Main routine             -]
[----------------------------------------]
T 64 K  [start loading at address 64 - start of tank 2]
G K     [store the @ code letter]

[-- Halt if (n = 0) --]

[00] A 0 G  [load LSD(n)]
[01] S 0 X  [subtract 1]
[02] E 7 @  [jump if positive or zero]
[03] A 1 G  [load MSD(n)]
[04] S 0 X  [subtract 1]
[05] E 7 @  [jump if positive or zero]
[06] Z F    [halt]

[-- Print the first line of the poem --]

[07] T 7 F  [clear the accumulator]
[08] A 46 F [load address of string 1]
[09] T 2 G  [store address of string 1 into variable 2]
[10] A 10 @ [load return address]
[11] G !    [call printing subroutine]

[-- Print the second line of the poem --]

[12] A 47 F [load address of string 2]
[13] T 2 G  [store address of string 2 into variable 2]
[14] A 14 @ [load return address]
[15] G !    [call printing subroutine]

[-- Set n := (n-1) --]

[16] A 0 G  [load LSD(n)]
[17] S 2 X  [subtract '1']
[18] U 0 G  [store LSD(n) but don't clear the accumulator]

[19] E 25 @ [jump if positive or zero]

[20] A 3 X  [add ''10'']
[21] T 0 G  [store '9' in LSD(n)]

[22] A 1 G  [load MSD(n)]
[23] S 2 X  [subtract '1']
[24] T 1 G  [store MSD(n)]

[25] T 4 G  [clear the accumulator]

[-- Print the third line of the poem --]

[26] A 48 F [load address of string 3]
[27] T 2 G  [store address of string 3 into variable 2]
[28] A 28 @ [load return address]
[29] G !    [call printing subroutine]

[-- Jump to the start of the loop --]

[30] E @    [go back to start of loop]


[----------------------------------------]
[-         Printing subroutine          -]
[-------------------------------------- -]
[- Takes one parameter in variable 2G,  -]
[- the address of the string to print.  -]
[----------------------------------------]
T 128 K  [start loading at address 128 - start of tank 4]

[-- Set up the return link --]

[00] A 3 F  [add base of return jump instruction]
[01] T 28 ! [store return jump instruction]

[-- Output the figure shift character --]

[02] O 5 X  [output figure shift]

[-- Output MSD(n) if (n > 9) --]

[03] A 1 G  [load MSD(n)]
[04] S 2 X  [subtract '1']
[05] G 7 !  [jump if negative]
[06] O 1 G  [output MSD(n)]

[-- Output LSD(n) --]

[07] O 0 G  [output LSD(n)]

[-- Print " BOTTLE" --]

[08] T 4 G  [clear the accumulator]
[09] A 49 F [load address of string 4]
[10] T 3 G  [store address of string 4 into variable 3]
[11] A 11 ! [load return address]
[12] G H    [call string printing subroutine]

[-- Print "S" unless (n = 1) --]

[13] A 1 G  [load MSD(n)]
[14] S 2 X  [subtract '1']
[15] E 22 ! [jump if positive or zero]

[16] T 7 F  [clear the accumulator]

[17] A 0 G  [load LSD(n)]
[18] S 2 X  [subtract '1']
[19] G 22 ! [jump if negative]
[20] S 2 X  [subtract '1']
[21] G 23 ! [jump if negative]

[22] O 4 X  [output 'S']

[-- Output the passed-in string --]

[23] T 4 G  [clear the accumulator]
[24] A 2 G  [load address of string from variable 2]
[25] T 3 G  [store address of string into address 1]
[26] A 26 ! [load return address]
[27] G H    [call string printing subroutine]

[-- Return --]

[28] P F    [modifiable - space for return jump instruction]


[----------------------------------------]
[-      String printing subroutine      -]
[----------------------------------------]
[- Takes one parameter in variable 3G,  -]
[- the address of the string to print.  -]
[----------------------------------------]
T 192 K  [start loading at address 192 - start of tank 6]

[-- Set up the return link --]

[00] A 3 F  [add base of return jump instruction]
[01] T 20 H [store return jump instruction]

[-- (beginning of loop) --]
[-- Create 'load' instruction --]

[02] A 3 G  [load address of next character to print]
[03] A 7 X  [add base of instruction to load next character]
[04] T 8 H  [store instruction to load next character]

[-- Create 'output' instruction --]

[05] A 3 G  [load address of next character to print]
[06] A 8 X  [add base of instruction to output next character]
[07] T 13 H [store instruction to output next character]

[-- Load next character and quit if it's the string terminator --]

[08] P F    [modifiable - space for instruction to load next character]

[09] S 6 X  [compare with terminator character]
[10] G 13 H [continue if negative]
[11] S 0 X  [subtract 1]
[12] G 19 H [exit if negative]

[-- Output the next character --]

[13] P F    [modifiable - space for instruction to output next character]

[-- Increment the string index --]

[14] T 4 G  [clear the accumulator]
[15] A 3 G  [load address of next character to print]
[16] A 1 X  [add 2]
[17] T 3 G  [store address of next character to print]

[-- Jump to the start of the loop --]

[18] E 2 H  [jump to beginning of loop]

[-- Return --]

[19] T 7 F  [clear the accumulator before returning]
[20] P F    [modifiable - space for return jump instruction]


[----------------------------------------]
[-              Constants               -]
[----------------------------------------]
T 256 K  [start loading at address 256 - start of tank 8]

[00] P D    [number - 1]
[01] P 1 F  [number - 2]

[02] Q F    [character - '1']
[03] J F    [character - ''10'' (i.e. '9' + '1')]
[04] S F    [character - S]
[05] # F    [character - figure shift]
[06] . F    [character - string terminator character]

[07] A F    [instruction - base for character load instruction]
[08] O F    [instruction - base for character output instruction]


[----------------------------------------]
[-              Variables               -]
[----------------------------------------]
T 288 K  [start loading at address 288 -  start of tank 9]

[00] O F    [variable - LSD(n) (initially '9')]
[01] O F    [variable - MSD(n) (initially '9')]
[02] P F    [variable - parameter to printing function]
[03] P F    [variable - parameter to string printing function]

[04] P F    [scrap area]


[----------------------------------------]
[-               String 1               -]
[----------------------------------------]
T 320 K  [start loading at address 320 - start of tank 10]

! F  [ ]
O F  [O]
F F  [F]
! F  [ ]
B F  [B]
E F  [E]
E F  [E]
R F  [R]
! F  [ ]
O F  [O]
N F  [N]
! F  [ ]
T F  [T]
H F  [H]
E F  [E]
! F  [ ]
W F  [W]
A F  [A]
L F  [L]
L F  [L]
# F  [figure shift]
N F  [,]
* F  [letter shift]
& F  [\n]
. F  [end]


[----------------------------------------]
[-               String 2               -]
[----------------------------------------]
T 384 K  [start loading at address 384 - start of tank 12]

! F  [ ]
O F  [O]
F F  [F]
! F  [ ]
B F  [B]
E F  [E]
E F  [E]
R F  [R]
# F  [figure shift]
M F  [.]
* F  [letter shift]
& F  [\n]
T F  [T]
A F  [A]
K F  [K]
E F  [E]
! F  [ ]
O F  [O]
N F  [N]
E F  [E]
! F  [ ]
D F  [D]
O F  [O]
W F  [W]
N F  [N]
# F  [figure shift]
N F  [,]
* F  [letter shift]
! F  [ ]
P F  [P]
A F  [A]
S F  [S]
S F  [S]
! F  [ ]
I F  [I]
T F  [T]
! F  [ ]
A F  [A]
R F  [R]
O F  [O]
U F  [U]
N F  [N]
D F  [D]
# F  [figure shift]
N F  [,]
* F  [letter shift]
& F  [\n]
. F  [end]


[----------------------------------------]
[-               String 3               -]
[----------------------------------------]
T 448 K  [start loading at address 448 - start of tank 14]

! F  [ ]
O F  [O]
F F  [F]
! F  [ ]
B F  [B]
E F  [E]
E F  [E]
R F  [R]
! F  [ ]
O F  [O]
N F  [N]
! F  [ ]
T F  [T]
H F  [H]
E F  [E]
! F  [ ]
W F  [W]
A F  [A]
L F  [L]
L F  [L]
# F  [figure shift]
M F  [.]
* F  [letter shift]
& F  [\n]
& F  [\n]
. F  [end]


[----------------------------------------]
[-               String 4               -]
[----------------------------------------]
T 512 K  [start loading at address 512 - start of tank 16]

* F  [letter shift]
! F  [ ]
B F  [B]
O F  [O]
T F  [T]
T F  [T]
L F  [L]
E F  [E]
. F  [end]

[----------------------------------------]
[-     Directives to initial orders     -]
[----------------------------------------]
E Z  [begin execution at code letter @]
P F

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Alternative Versions

VersionAuthorDateCommentsRate
1James Lingard05/08/072
2James Lingard05/21/060

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