Program To Count Length Of String And Display It In LC3 Assembly Language Assignment Solution

Instructions

Objective

Write an assembly language assignment program to count length of string and display it in LC3

Requirements and Specifications

Write an assembler program that prompts a user to input some type of string. It can be anything from a famous sentence, a song lyric, saying, etc. Then write and call a function that will count the number of characters entered and return the number of characters entered back to the main program. The main program will then tell the user how many characters they had entered. You don't need to worry about spaces, commas, periods, etc. Everything typed can be considered a character.

Remember, there is a difference between an integer representation of a number and the character representation of a number. i.e. To print the number 31 you need to print the character 3 which is ×33 in ASCII and 1 is x31 in ASCII.

If you initialise any memory locations or registers, make sure you comment that at the beginning of your code.

Screenshots of output

Source Code

.ORIG x3000 MAIN ; Prompt user to enter string LEA R0, PROMPT ; load address of prompt PUTS ; print the prompt ; Count characters in string JSR COUNTCHARS ; count characters in string ; Convert number to ascii LEA R4, NUMBER ; load address to save number AND R2, R2, #0 ; start in zero STR R2, R4, #0 ; save ending zero CONVNUM AND R2, R2, #0 ; quotient, start in zero DIV10 ADD R3, R0, #-10 ; compare number with 10 BRn SAVEDIGIT ; if less than 10, save digit ADD R2, R2, #1 ; else, increment quotient ADD R0, R3, #0 ; copy subtraction to number BR DIV10 ; repeat SAVEDIGIT LD R3, ASCII0 ; load ascii 0 ADD R0, R0, R3 ; convert digit to ascii ADD R4, R4, #1 ; increment position in converted string STR R0, R4, #0 ; save converted digit ADD R0, R2, #0 ; copy quotient to R0 BRp CONVNUM ; if not zero, convert next digit ; Print result message LEA R0, RESULT ; load address of result string PUTS ; print the string ; Print number PRINTDIGIT LDR R0, R4, #0 ; load digit from converted number BRz PRINTEND ; if it's zero, end print OUT ; else, print digit ADD R4, R4, #-1 ; go to previous digit BR PRINTDIGIT ; print next digit PRINTEND HALT ; terminate the program ; Data for main PROMPT .STRINGZ "Please enter a string: " RESULT .STRINGZ "Number of characters entered: " ASCII0 .FILL 48 ; ascii value of '0' NUMBER .BLKW 10 ; space to save converted number digits ; Function to count characters in a string ; Returns: ; R0 = count of characters COUNTCHARS ST R7, SAVER7 ; save return address AND R2, R2, #0 ; start count in zero CNTLOOP GETC ; read character OUT ; echo on screen ADD R1, R0, #-10 ; compare character with enter BRz CNTEND ; if equal, end reading string and end count ADD R2, R2, #1 ; else, count one more char BR CNTLOOP ; count next character CNTEND ADD R0, R2, #0 ; return count in R0 LD R7, SAVER7 ; load return address RET ; return to calling function ; Data for countchars SAVER7 .BLKW 1 ; place to save R7 .END