Chapter 4, Problem 42E

Explanation of Solution

Trace out for given “Example 4.4”:

Tracing the program is the process of documenting the state of the various aspects of the execution of the program over assembly instruction. Every instruction has the process like fetch, store, and decode which are used to determine the desired outcome to execute the program.

This tracing has address, label, instruction, RTN, and values of each registers. The following table has the final status of each instruction execution.

The trace out for given code “example 4.4” is as follows:

Address	Label	Step	RTN	PC	IR	MAR	MBR	AC
100	Getch	LoadI Chptr	MARßPC IRß M[MAR] PCßPC+1 MARßIR[11-0] MBRßM[MAR] MARßMBR MBRßM[MAR] ACßMBR	101	D10A	100 10A 10B	010B 0048	0048
101		Skipcond 400	MARßPC IRß M[MAR] PCßPC+1 If IR[11-0]==00 then If AC<0 then PCßPC+1 Else if IR[11-0]=01 then If AC=0 then PCßPC+1 Else if IR[11-0]=10 then If AC>0 then  PCßPC+1	102	8400	101
102		Jump Outp	MARßPC IRß M[MAR] PCßIR[11-0]	104	9104	102
103		Halt
104	Outp	Output	MARßPC IRß M[MAR] PCßPC+1 OutRegßAC	105	6000	104
105		Load chptr	MARßPC IRß M[MAR] PCßPC+1 MARßIR[11-0] MBRßM[MAR] ACßMBR	106	11A	105 10A	010B	010B
106		Add One	MARßPC IRß M[MAR] PCßPC+1 MARßIR[11-0] MBRßM[MAR] ACßAC+MBR	107	3109	106 109	0001