Chapter 6, Problem 39E

Explanation of Solution

Program code:

LDA   0X0048,i ;Load character "H" in the accumulator

STA   0X008B,d ;Store contents of accumulator in 8B

CHARO 0X008C,d ;Read character from specified location and ;Write on the screen

LDA   0X0065,i ;Load character "e" in the accumulator

STA   0X008B,d ;Store contents of accumulator in 8B

CHARO 0X008C,d ;Read character from specified location and ;Write on the screen

LDA   0X006C,i ;Load character "l" in the accumulator

STA   0X008B,d ;Store contents of accumulator in 8B

CHARO 0X008C,d ;Read character from specified location and ;Write on the screen

LDA   0X006C,i ;Load character "l" in the accumulator

STA   0X008B,d ;Store contents of accumulator in 8B

CHARO 0X008C,d ;Read character from specified location and ;Write on the screen

LDA   0X006F,i ;Load character "o" in the accumulator

STA   0X008B,d ;Store contents of accumulator in 8B

CHARO 0X008C,d ;Read character from specified location and ;Write on the screen

STOP     ;Stop processing

.END         ;End program

Explanation:

The above program code is used to write the word “Hello” on the screen by using direct addressing mode.

• In the direct addressing mode, the operand in the instruction contains the address of the data which is needed to load into the accumulator.
• As it follows 16-bit addressing, while writing a character, it writes the next address of the loaded location.

In the program code:

• To write the character “H”,
  • It loads the hexadecimal value “(0X0048)” of the character “H” into the accumulator.
  • And it stores the content of the accumulator into the specified location “8B”...