LC-3 Assembly Language /

Take countChars.asm and modify it to input the string to be searched and to output the count with an appropriate output message.

_______ countChars.asm reference file ________

; countChar.asm ; Program to count occurrences of a character in a string. ; R0 - Character input from the keyboard. ; R1 - Character loaded from memory ; R2 - Count of occurrences, start at 0 ; R3 - Pointer to block of characters ; Result displayed on the console. ; Program only works if no more than 9 occurrences are found.

.ORIG x3000 BR Start

ASCII .FILL x30 ; offset to convert to ascii STRING .STRINGZ "Now is the time for all good men to come to the aid of their country."

Start AND R2, R2, #0 ; R2 is counter, initially 0 LEA R3, STRING ; R3 is pointer to string IN ; R0 gets character input NOT R0, R0 ; Calculate two's complement ADD R0, R0, #1 LDR R1, R3, #0 ; R1 gets first character in string

TEST BRz OUTPUT ; If R1=0, prepare the output ADD R1, R1, R0 ; Compare characters BRnp GETCHAR ; If no match, do not increment ADD R2, R2, #1 ; Otherwise, increment count

GETCHAR ADD R3, R3, #1 ; Point to next character. LDR R1, R3, #0 ; R1 gets next char to test BR TEST

OUTPUT LD R0, ASCII ; Load the ASCII offset ADD R0, R0, R2 ; Covert binary count to ASCII OUT ; ASCII code in R0 is displayed. HALT ; Halt machine .END