Assembly language code lab 2

 Lab 2 adding calculator 

About: 

The Adding Calculator program is designed for a computer system with specific memory locations and routines. The program prompts the user to enter two decimal numbers, performs addition, and displays the sum.

Code:

; Adding Calculator ; ROM routine entry points define SCINIT $ff81 ; initialize/clear screen define CHRIN $ffcf ; input character from keyboard define CHROUT $ffd2 ; output character to screen ; zeropage variables define PRINT_PTR $10 define PRINT_PTR_H $11 define firstInput $14 define secInput $15 ; absolute variables define GETNUM_1 $0080 define GETNUM_2 $0081 define ENTER $0d ; for the ENTER key define BACKSPACE $08 ; for the BACKSPACE key ; -------------------------------------------------------- ; Main loop jsr SCINIT ; initialize/clean screen main: ; get first input' ldy #$00 jsr firstInputQs ; ' jsr GETNUM ; get firstInput sta firstInput ; store firstInput ; get second input' ldy #$00 jsr secondInputQs ; ' jsr GETNUM ; get secondInput sed ; sets decimal model flag in processor status register clc ; clear carry flag in status register adc firstInput ; add with carry cld ; clear decimal mode flag sta firstInput ; store result bcc result ; if carry flag=0 -> branch to result inc secInput ; increment ; get sum result result: pha ; push current value onto the stack' ldy #$00 jsr showResultMsg ; ' lda secInput beq low_digits ; if result=0 -> branch to low-digits lda #$31 jsr CHROUT jmp draw_100s low_digits: lda firstInput and #$f0 ; keep high nibble, masking out low nibble beq ones_digit ; if high nibble=0 -> branch to ones_digit draw_100s: lda firstInput lsr ; logical shift right lsr lsr lsr ora #$30 ; add ASCII value for 0 for conversion to char jsr CHROUT ones_digit: lda firstInput and #$0f ora #$30 jsr CHROUT ; initialize green pointer' ldx #$00 stx $10 stx $11 ; ' jsr display_green jsr main ; -------------------------------------------------------- ; Print a message PRINT: pla ; pull the value from stack -> accumulator clc ; clear carry flag adc #$01 ; add with carry sta PRINT_PTR pla ; retrieves a byte from stack -> accum sta PRINT_PTR_H tya ; transfer y to accumulator pha ; store value in accumulator -> stack ldy #$00 ; load y register with 0 print_next: lda (PRINT_PTR),y ; load PRINT_PTR, Y into accumulator beq print_done jsr CHROUT iny jmp print_next print_done: tya clc adc PRINT_PTR sta PRINT_PTR ; store the result in PRINT_PTR lda PRINT_PTR_H ; load value at PRINT_PTR_H -> accumulator adc #$00 ; add zero sta PRINT_PTR_H ; store the result in PRINT_PTR_H pla tay ; transfer accumulator to Y lda PRINT_PTR_H pha ; push accumulator to stack lda PRINT_PTR pha rts ; return ; --------------------------------------------------- ; GETNUM - get a 2-digit decimal number ; ; Returns A containing 2-digit BCD value GETNUM: txa ; transfer x register -> accumulator pha ; push accumulator value -> stack tya ; transfer y register -> accumulator pha ldx #$00 ; count of digits received stx GETNUM_1 ; store value of x into $0080 stx GETNUM_2 ; store value of x into $0081 getnum_cursor: lda #$a0 ; black square jsr CHROUT lda #$83 ; left cursor jsr CHROUT key_check: jsr CHRIN cmp #$00 beq key_check ; if 0 -> loops back cmp #BACKSPACE ; comps value w/BACKSPACE beq getnum_bs cmp #ENTER ; comps value w/ENTER beq getnum_enter cmp #$30 ; "0" bmi key_check ; if result of comps=negative cmp #$3a ; "9" + 1 bmi getnum_digit jmp key_check getnum_enter: cpx #$00 ; compare x with 0 beq key_check ; if 0 -> branch lda #$20 jsr CHROUT lda #$0d jsr CHROUT lda GETNUM_1 cpx #$01 ; comps x register with 1 beq getnum_done asl ; multiples value * 2 asl asl asl ora GETNUM_2 ; logical OR ops getnum_done: sta GETNUM_1 pla ; pull top value from stack -> accumulator tay ; transfer accumulator -> y pla tax ; transfer accum -> x lda GETNUM_1 rts ; return getnum_digit: cpx #$02 ; comps x value with 2 bpl key_check ; if positive -> branch pha ; push accu -> stack jsr CHROUT pla and #$0f ; bitwise AND ops sta GETNUM_1,x inx jmp getnum_cursor getnum_bs: cpx #$00 beq key_check lda #$20 jsr CHROUT lda #$83 jsr CHROUT jsr CHROUT lda #$20 jsr CHROUT lda #$83 jsr CHROUT dex lda #$00 sta GETNUM_1,x jmp getnum_cursor ; --------------------------------------------------- ; print questions' fistInput: dcb $0d,$0d,"E","n","t","e","r",32,"a",32,"F","I","R","S","T",32,"N","U","M","B","E","R" dcb "(","0","-","9","9",")",":" dcb 32,32,32,32,32,32,32,00 secondInput: dcb "E","N","T","E","R",32,"S","E","C","O","N","D",32,"N","U","M","B","E","R" dcb "(","0","-","9","9",")",":" dcb 32,32,32,32,32,32,32,32,00 sumResult: dcb "S","u","m",32,"R","e","s","u","l","t",":",32,32 dcb 32,32,32,32,32,32,32 dcb 32,32,32,32,32,32,32 dcb 32,32,32,32,32,32,32 dcb 00 firstInputQs: lda fistInput,y beq backToMain jsr CHROUT iny bne firstInputQs secondInputQs: lda secondInput,y beq backToMain jsr CHROUT iny bne secondInputQs showResultMsg: lda sumResult,y beq backToMain jsr CHROUT iny bne showResultMsg backToMain: rts ; --------------------------------------------------- ; display green color when result is available display_blue: lda #$06 ; Load a with colour code ldy #$00 ; load the Y register with 0 color_loop: sta ($10), y ; add y to pointer at $10 and store the accumulator there iny ; increment the y register y++ bne color_loop ; continue until page 2 is done inc $11 ; increment high byte (page) of pointer cpx $11 ; compare value in X register with page number 6 bne color_loop ; continue as long as we have not hit the page 6. rts ;'

Here's a brief overview of its functionality:

The program initializes by clearing the screen and setting up variables. It repeatedly prompts the user to enter the first and second numbers. Upon receiving each number, it processes the input and stores it in memory.

After obtaining both numbers, the program performs addition using binary-coded decimal (BCD) arithmetic. It adds the two numbers digit by digit, handling carries appropriately.

Once the addition is complete, the program displays the sum on the screen. It first checks if the sum is zero. If not, it starts converting and displaying each digit of the sum.

Additionally, the program includes routines to handle backspace and enter keys during input, ensuring a smooth user experience.

Furthermore, it utilizes specific memory addresses for storing data, displaying messages, and managing program flow.

The display_blue subroutine is responsible for changing the color of the text to blue to indicate that the result is available.

In summary, the Adding Calculator program efficiently handles user input, performs addition accurately, and provides visual feedback to the user, making it a functional tool for basic arithmetic operations.