Chapter 6, Problem 52E

Explanation of Solution

Button for keyboard input on Pep/9 console:

The Pep/9 simulator contains the “Terminal I/O” button to get the input values from the user while executing the program.

Example program:

Consider the following assembly-language program which is used to perform arithmetic operations on the three input variables “number1”, “number2”, and “number3”.

Symbol	Mnemonics	Operand	Comment
	BR	Main	; Branch around data
number1:	.BLOCK	2	; Set up a two-byte block for number1
number2:	.BLOCK	2	; Set up a two-byte block for number2
number3:	.BLOCK	2	; Set up a two-byte block for number3
result:	.BLOCK	2	; Set up a two-byte block for result
Main:	DECI	number1,d	; Read and store number1
	DECI	number2,d	; Read and store number2
	DECI	number3,d	; Read and store number3
	LDA	number1,d	; Load number1 value into the accumulator
	ADDA	number3,d	; Add number3 to accumulator and store output into the accumulator
	SUBA	number2,d	; Subtract number2 from the accumulator and store output into the accumulator
	STA	result,d	; Store accumulator value into result
	DECO	result,d	; Write result value on the screen
	STOP		; Stop the processing
	...