Assignment - MARIE & ISA

Task-

Q1. A digital computer has a memory unit with 16 bits per word. The instruction set consists of 122 different operations. All instructions have an operation code part (opcode) and an address part (allowing for only one address). Each instruction is stored in one word of memory.

a) How many bits are needed for the opcode?

b) How many bits are left for the address part of the instruction?

c) What is the maximum allowable size for memory?

d) What is the largest unsigned binary number that can be accommodated in one word of memory?

Q2. Consider the MARIE program below.

a) List the hexadecimal code for each instruction.

b) Draw the symbol table.

c) What is the value stored in the AC when the program terminates?

Hex

Addr Label          Instruction

100 Start,             Load A

101                         Add B

102                         Store Temp

103                         Load C

104                         Add D

105                         Add Temp

106                         Store F

107                         Output

108                         HALT

109    A,                 DEC 5

10A    B,                DEC 3

10B     C,                DEC 4

10C     D,               DEC 13

10D     E,                DEC 3

10E   Temp,      HEX 00FD

10F     F,                HEX 00FE

Q3. Write code to implement the expression

F = (A+B) /(C*D*E) on 2-, 1- and 0-address machines.