1. Chapter # 6
PROGRAMING
THE BASIC COMPUTER

2. Contents Machine language Assembly language The Assembler
Program Loops
Programming Arithmetic and Logic Operations
Subroutines
Input-Output Programming

3. Table 6-1 Computer Instruction
Sym
I= I=1
Description
AND
0xxx
8xxx
And Memory to AC
ADD
1xxx
9xxx
Add Memory to AC
LDA
2xxx
Axxx
Load To AC
STA
3xxx
Bxxx
Store Of AC
BUN
4xxx
Cxxx
Branch Uncondionary
BSA
5xxx
Dxxx
Return Address
ISZ
6xxx
Exxx
Skip If Zero

4. CLA 7800 Clear AC Clear E Comp. AC Comp. E Cir. Right AC and E
Table 6-1 Instruction
CLA
7800
Clear AC
Clear E
Comp. AC
Comp. E
Cir. Right AC and E
Cir. Left AC and E
Increment AC
Skip If AC is Positive
Skip If AC is Negative
Skip If AC is Zero
Skip If E is 0
Halt Computer
CLE
7400
CMA
7200
CME
7100
CIR
7080
CIL
7040
INC
7020
SPA
7010
SNA
7008
SZA
7004
SZE
7002
HLT
7001

5. Instruction For Computer
INP
F800
Input to AC
OUT
F400
Output From Ac
SKI
F200
Skip on Input Flag
SKO
F100
Skip On Output Flag
ION
F080
Interrupt On
IOF
F040
Interrupt Off

6. Table 6-4 Symbolic Operation Code
Location Instruction Comments
LDA Load First operand In AC
ADD Add second operand to Ac
STA Store in location 006
HLT Halt Computer
First Operand
FFE Second Operand is Negative
Store Sum Here

7. Table 6-3 Hexadecimal Add two Number
Location Instruction
FFE9

8. Table 6-2 Binary to Add Two Numbers
Location Instruction Code

9. Table 6-5 Assembly Language Program
ORG Origin is 0
LDA A Load operation A
ADD B Add operation B
STA C Store Location C
HLT Halt Computer
A, DEC Decimal Operand
B, DEC – Decimal Operand
C, DEC Store in Location C
END End Of Program

10. Table 6-6 Fortran Program to ADD Two Number
Integer A, B, C
Data A, 83 B, -23
C = A+B
End

11. Table 6-7 Definition Of Pseudoinstructions
Symbol Information For Assembler
ORG N N operation for hexadecimal
operand listed line.
END End of Program
DEC N N converted to Binary
HEX N Hexadecimal Converted to Binary

12. Instruction Field of Program
CLA NON-MRI
ADD OPR DIRECT ADDRESS MRI
ADD PTR I INDIRECT ADDRESS MRI

13. Table 6-8 Assembly language program subtract Two number
ORG ORIGIN LOCATION IS 100
LDA SUB LOAD TO AC
CMA COMPLEMENT AC
INC INCREMENT AC
ADD MIN ADD TO AC
STA DIF STORE DIFFERENCE
HLT HALT COMPUTER
MIN, DEC MINUEND
SUB, DEC – SUMTRAHEND
DIF, HEX DIFFERENCE STORE HERE
END END PROGRAM

14. Table 6-9 translated program of table 6-8
HEXADECIMAL
LOCATION CINTENT SYMBOLIC PROGRAM
ORG 100
LDA SUB
CMA
INC
ADD MIN
STA DIF
HLT
MIN, DEC 83
FFE SUB, DEC -23
DIF, HEX0
END

15. ADDRESS SYMBOL HEXADECIMAL MIN 106 SUB 107 DIF 108
Address symbol Table
ADDRESS SYMBOL HEXADECIMAL
MIN
SUB
DIF

16. Table 6-11 line of code: pl3, ld,sub1
Memory word symbol hex-code binary represent
1 PL AC
2 3, C
3 L D C
4 A
5 SU
6 B
7 I CR OD

17. Figure 6-1 First pass of assemblerLC
Scan line code
Set LC
Yes
Label
ORG No No
Yes
End
Yes
Store symbol
in Address symbol
With Ac
Go to second
pass No
Increment LC

18. MEMORY SYMBOL HEX-CODE Binary rep.. WORD ( LC )
Table 6-12 Address symbol
MEMORY SYMBOL HEX-CODE Binary rep..
WORD ( LC )
M I D
N , E 2C
(LC)
S U
B , C
(LC) DI
F C
(LC)

19. Figure 6-2 Flowchart for second pass of assemblerLC
DONE
Scan next line of code
Set LC
yes
yes
Pseudo
instruction
ORG no
END
yes no
DEC or HEX no
yes
MRI no
Convert operand
To binary and store
In location
Given by LC
Get operation code
and set bits
2-4
Valid
Non-MRI
instruction no
Search address symbol
Table for binary equivalent
Of symbolic address
And set bits 5-16
yes
Store binary
Equivalent of
Instruction
In loaction given
By LC
Error in line
Of code
yes no I
Set first
bit to 1
Set first
Bit to 0
Assemble all parts and store
In location give by LC
Increment LC

20. Table 6-13 Program to Add 100 Number
Line 1 2 3 4 5 6
7 Lop, 8 9 10
13 ADS,
14 PTR,
15 NBR,
16 CTR,
17 SUM,
118
119
Org 100
LDA ADS
STA PTR
LDA NBR
STA CTR
CLA
ADD PTR1
ISZ PTR
ISZ CTR
BUN LOP
HEX 150
HEX 0
DEC –100
DEC 23
END
/ Origin is HEX 100
/ Load First Address Of Operand
/ Store in Pointer
/ Load Minus 100
/ Store in Counter
/ Clear Ac
/ Add To Ac
/ Inc Pointer
/ Inc Counter
/ Loop Again
/ First Address Of Operand
/ Reserved for Pointer
/ Initialized Counter
/ Reserved For Counter
/ Sum is Stored Here
/ Last Operand
/ End Program

21. Figure 6-3 Flowchart For Multiplication ProgramX= Y=
CTR P P
E 0
AC Y
cir EAC
Y AC
Cil EAC =0 =1 E
X AC
P P+X E
CTR CTR+1
AC X
CTR #0 =0
Stop

22. Table 6-15 Add Two Double Precision
LDA AL /Load a Low
ADD BL /Add B low ,Carry In E
STA CL /Store in C Low
CLA /Clear Ac
CIL /Carry into Ac
ADD Ah /A high and carry
ADD BH /Add B high
STA CH /Store in C High
HLT
AL, ____ /Location Of Operand
AH, _____
BL, _____
BH, ______
CL, _______
CH, _________

23. Table 6-16 Demonstrates the use of subroutines
Location
100
101
102
103
104
105
107 X,
108 Y,
109 SH4
10A
10B
10C
10D
10E
10F
110 MSK,
ORG 100
LDA X
BSA SH4 STA X
LDA Y
BSA SH4
STA Y
HLT
HEX 1234
/Main Program
/Load X
/Branch to Subroutine
/Store shifted Number
/Load Y
/Branch To Subroutine
/Store Shifted Number
/Shift Left 4 Times
/Store return Address here
/Cir Left Once
/Cir Left Forth Times
/Set Ac(13—16) To Zero
Return To Main Program
/Mask Operand
HEX FFF0
CIL
CIL
CIL
CIL
AND MSK
BUN SH4
HEX FFF0
END

24. Table 6-20 Input pack to characters
IN2, ________ /Subroutine entry
FST, SKI
BUN FST
INP /Input first character
OUT
BSA SH /Shift 4 times
BSA SH4 /Sift 4 more times
SCD, SKI
BUN SCD
INP /Input second Character
BUN IN21 /Return

25. Table 6-21 Program Input Character in a Buffer
LDA ADS /LOAD IN BUFFER
STA PTR /INITIALIZE POINTER
BSA IN /GO IN IN2
STA PTR / STORE IN BUFFER
ISZ PTR / INCREMENT POINTER
BUN LOP /INPUT MORE CHRACTER
HLT
HEX /FIRST ADRESS OF BUFFER
HEX /LOCATION FOR POINTER.
LOP,
ADS,
PTR,

26. Table 6-22 Compare Two Words
LDA WD /LOAD FIRST WORD
CMA
INC /FORM 2’S COMPLEMENT
ADD WD /ADD SECOND WORD
SZA /SKIP IF AC IS ZERO
BUN UEQ /UNEQUAL ROUTINE
BUN EQL /EQUAL ROUTINE
_____
WD1,
WD2,

27. Table 6-19 Input-Output One Character
(a) Input a Character:
CIF, SKI /CHECK INPUT FLAG
BUN CIF /FLAG=0
INP /FLAG=1
OUT /PRINT CHARACTER
STA CHR /STORE CHARACTER
HLT
CHR, ____ /STORE CHARACTER
(b) Output one character:
LDA CHR /LOAD INTO AC
COF, SKO /CHECK OUTPUT FLAG
BUN COF /FLAG=0
OUT /FLAG=1
CHR, HEX /CHARACTER IS “W”

28. Table 6-23 program to service an Interrupt
Location
ZERO, _______ /RETURN ADDRESS
BUN SRV /BRANCH ROUTINE
CLA /RUNING PROGRAM
ION /TURN ON FACILITY
LDA X
ADD Y /INTERRUPT HERE
STA Z /PROGRAM RETURN HERE
/INTERRUPT ROUTINE S
200 SRV, STA SAC /STORE AC
CIR /MOVE E INTO AC(1)
STA SE /STORE OF E
SKI /CHECK INPUT FLAG
BUN NXT /FLAG IS OFF
INP /FLAG IS ON
OUT /PRINT FORM
STA PT /STORE BUFFER
ISZ PT /INC INPUT POINTER
NXT, SKO /OUTPUT FLAG
BUN EXT / FLAG IS OFF
LDA PT /INC OUTPUT POINTER

29. Table 6-23 program to service an Interrupt
ISZ PT /INC INPUT POINTER
LDA SE /RESERVE VALUE
CIL /SHIFT IT TO E
LDA SAC /RESTORE AC
ION ZR /RETURN TO PROGRAM
_____ /AC IS STORE HERE
______ /E IS STORED HERE
_______ / POINTER OF INPUT BUFFER
_________ /OUTPUT BUFFER
EXT,
SAC,
SE,
PT1
PT2,