计算机系统1--原书第六章答案

Appendix F

Selected Solutions

F.6 Chapter 6 Solutions

6.1 Yes, for example, an iterative block where the test condition remains true for each iteration.

This procedure will never end and is therefore not finite and not an algorithm. The following

is an example of a procedure that isn’t an algorithm:

x3000 0101 000 000 1 00000 ( LOOP AND R0, R0, #0 )

x3001 0000 010 111111110 ( BRz LOOP )

This is not an algorithm because the branch instruction is always taken and the program loops

x3003 0001010010100001 ( ADD R2, R2, #1 )

x3004 0001001001111111 ( L ADD R1, R1, #-1 )

x3005 0000100000000010 ( BRn D )

x3006 0001010010000010 ( ADD R2, R2, R2 )

x3007 0000111111111100 ( BRnzp L )

x3008 0001001010100000 ( D ADD R1, R2, #0 )

x3009 1001000000111111 ( NOT R0, R0 )

x300a 1001001001111111 ( NOT R1, R1 )

x300b 0101000000000001 ( AND R0, R0, R1 )

x300c 1001000000111111 ( NOT R0, R0 )