PROGRAM TO CALCULATE AREA AND CIRCUMFERENCE OF A CIRCLE(ASM)

;AUTHOR: ANUEBUNWA VICTOR OGECHUKWU
;PROGRAM TO CALCULATE AREA AND CIRCUMFERENCE OF A CIRCLE IN 8086 ASSEMBLY
;ASSEMBLER: MASM

.MODEL SMALL
.STACK
.DATA
            PIx100 EQU 314          ;PI(approximated to 2dp) * 100
            MSG1 DB "Enter radius: ",'$'
            MSG2 DB 0AH,0DH,"The area of the circle is: ",'$'
            MSG3 DB 0AH,0DH,"and it's circumference is: ",'$'
            AREA DW ?
            CIRCUMFERENCE DW ?
            VALUE DW ?
.CODE
start:      MOV AX, @data
            MOV DS, AX

            MOV AH, 09H     ;Print string function
            LEA DX, MSG1
            INT 21H
            MOV AH, 3FH     ;Input string function
            LEA DX, VALUE
            INT 21H
            LEA SI, VALUE
            CALL CHAR2INTR      ;Converts collected characters to an integer and stores result in AX

                        ;Calculating Area
            MOV VALUE, AX
            MUL VALUE       ;raduis * radius
            MOV BX, PIx100
            MUL BX          ;(radius * radius) * (PI*100)
            MOV BX, 100     ;Subroutine displayReal requires that you multiply value by 100 before division (to move value dp up 2 places)
            MUL BX          ;i.e 4.230 * 100 = 423.0 (Moving dp up 2 places)
                        ;dp will be placed at its appropriate position during display(in subroutine displayReal)
            MOV BX, 100
            DIV BX          ;(radius * radius) * (PI*100)/100 = (radius * radius) * PI
            MOV AREA, AX        ;Stores result

                        ;Calculating Circumference
            MOV AX, VALUE
            MOV BX, 2
            MUL BX          ;raduis * 2
            MOV BX, PIx100
            MUL BX          ;(radius * 2) * (PI*100)
            MOV BX, 100
            MUL BX          ;Moving dp up 2 places
            MOV BX, 100
            DIV BX          ;(radius * 2) * (PI*100)/100 = (radius * 2) * PI
            MOV CIRCUMFERENCE, AX   ;Stores result

            MOV AH, 09H
            LEA DX, MSG2
            INT 21H
            MOV AX, AREA
            CALL DISPLAYREAL    ;Displays Area

            MOV AH, 09H
            LEA DX, MSG3
            INT 21H
            MOV AX, CIRCUMFERENCE
            CALL DISPLAYREAL    ;Displays Circumference


            MOV AH, 4CH
            INT 21H         ;Program terminates

CHAR2INTR PROC
            PUSH BX
            PUSH CX
            PUSH DX
            PUSH SI
            PUSHF

            MOV AX, 0000H
            MOV CX, 0000H
CLOOP1:     MOV AX, [SI]            ;Loads character currently pointed to into AX
            CMP AL, '9'
            JNLE XCLOOP1        ;Exits loop if character is not less or equal to '9'
            CMP AL, '0'
            JNGE XCLOOP1        ;Exits loop if character is not greater or equal to '0'
            INC CL          ;Else, Keeps count of the number of characters being processed
            INC SI          ;Moves pointer to the next character
            SUB AL, 30H     ;Converts character to digit
            PUSH AX         ;Pushes digit to stack
            JMP CLOOP1      ;continues loop

XCLOOP1:    MOV BX, 0001H
            MOV DX, 0000H
CLOOP2:     CMP CL, 0           ;Checks number of characters processed
            JE XCLOOP2      ;Exits loop if no character was processed i.e CL = 0
            POP AX          ;Else, pops digit from stack to AX
            MUL BL          ;Multiplies digit with it's PLACEMENT-VALUE. RECALL: unit = 1, tens = 10, hundreds = 100 ...
            ADD DX, AX      ;Adds (digit * PLACEMENT-VALUE)s together. RECALL: 234 = (4 * 1) + (3 * 10) + (2 * 100) where 1,10,100 represent their PLACEMENT-VALUES
            MOV AX, 10
            MUL BL          ;Multiplies current PLACEMENT-VALUE by 10 to advance to the next PLACEMENT-VALUE.
            XCHG AX, BX     ;Puts result from multiplication back to BX
            DEC CX          ;Reduces count
            JMP CLOOP2      ;Loop continues

XCLOOP2:    MOV AX, DX          ;Moves converted value to AX

            POPF
            POP SI
            POP DX
            POP CX
            POP BX
            RET
CHAR2INTR ENDP
;End of Subroutine CHAR2INTR

displayReal PROC
            PUSH AX
            PUSH BX
            PUSH CX
            PUSH DX
            PUSHF
            MOV BX, 10      ;Initializes divisor
            MOV DX, 0000H
            MOV CX, 0000H
.tryloop3:  MOV DX, 0000H
            DIV BX          ;Divides AX by 10
            PUSH DX         ;Pushes DX(remainder) to stack
            INC CX          ;Increments counter to track the number of digits
            CMP AX, 0       ;Checks if there is still something in AX to divide
            JNE .tryloop3       ;Jumps if AX is not zero

            SUB CX, 2       ;Moves back two decimal places

.tryloop4:  POP DX              ;Pops from stack to DX
            ADD DX, 30H     ;Converts to it's ASCII equivalent
            MOV AH, 02H
            INT 21H         ;calls DOS to display character
            LOOP .tryloop4      ;Loops till CX equals zero

            MOV DL, '.'
            MOV AH, 02H
            INT 21H         ;Places a dot

            MOV CX, 0002H
.tryloop5:  POP DX              ;Pops from stack to DX
            ADD DX, 30H     ;Converts to it's ASCII equivalent
            MOV AH, 02H
            INT 21H
            LOOP .tryloop5      ;Loops to display the decimal parts
            POPF
            POP DX
            POP CX
            POP BX
            POP AX
            RET         ;returns control
displayReal ENDP

END start
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