CPU receives signal from input device specifying the first input string is (00111000)ready.

The operating system copies the input string into one of its internal buffers.(00111000)

Operating system signals program that input is ready.

Program reads input string(00111000) from operating system buffer into program input string storage.

Program converts input string(001110000) into internal representation which (0001000)it stores in location A.

Repeat of steps 1 through 4 for second input string.

CPU receives signal from input device specifying the first input string is ready.(00111000)

The operating system copies the input string into one of its internal buffers.(00111000)

Operating system signals program that input is ready.

Program reads input string from operating system buffer into program input string storage.(001110000)

Program converts second input string into internal representation which it stores in location B.

Program copies data in A into first ALU register.

Program copies data in B into second ALU register.

Program executes ALU add instruction.

Program moves data in ALU accumulator into program storage location S.

Program converts data in location S into output string.

Program sends output string to operating system to be displayed. Operating system copies program output string into internal buffer.

Operating system sends output string from internal buffer to output device.