EECS113 Homework 2

char string1[ ] = “your test string”; // null terminated

char string1Len = 16;

char string2[ ] = “”;

char string2Len = 0;

// Append the length after the null character

// Try five strings, different lengths etc

char   t = 0; // Global (in a register) tracking test cases

char strcpy ( char *s, char * sd ) {

char len = 0;

while(s[len] != ‘\0’) {

sd[len]=s[len]; // Another variable in another memory location

++len;

}

return len;

}

void testString( char *s) {

char* sd;

char len = strcpy( s, sd );

char expectedLen = s[len+1];

char* expectedstr = sd;

if ( len != expectedLen ) goto Error;

if ( strcmp( expectedstr, s ) != 0 ) goto Error;

t++;

}

void main() {

testString(string1);

testString(string2);

…. // More test cases

SUCCESS:  goto SUCCESS;

ERROR:      goto ERROR;
}

;; Put status of your code here: does it work? has bugs? etc

;; If it doesn’t work, what do you think is wrong with it?

ORG 0H
SJMP  MAIN

STRING1:  DB “your test string” ;; string data

DB 0  ;; Null termination

STRING1LEN: 16  ;; String length follows the null

STRING2:  DB  …….

STRCPY:

;; The caller passes source string pointer in DPTR (in ROM).

;; The caller passes destination string pointer in R0 (in RAM).

;; The caller expects return value in accumulator A

;; DPTR and R0 should not be modified.

;; This function may safely use R1 without saving

;; Initialize the len variable

;; Load each character from source string’s memory.

;; Q: Which memory? MOV? MOVX? MOVC?

;; Check to make sure it is not the null character

;; If it is null, return the len in A; otherwise, increment count and save the character to the corresponding RAM location.

;; Declare your own labels as needed.

TESTSTRING:

;; The purpose is to call STRCPY, fetch the answer

;; (which follows the string data; e.g., STRING1LEN)

;; and compare if they are the same.

;; If the length is different from the expected length

;; then jump to ERROR.

;; Else Compare the copied data with the original (loop over length)

;; If one character does not match

;; then jump to ERROR.

;; Otherwise, increment the global variable t

;; to advance to the next test case

;; You can use CALL  pseudocinstruction, and the

;; assembler automatically selects ACALL or LCALL

;; You may trash registers R3 without saving.

MAIN:

;; Use R2 as the variable t, initialize to 0

;; Load the address of STRING1 to DPTR

;; Call TESTSTRING

;; Load the address of STRING2 to DPTR

;; Call TESTSTRING

SUCCESS: SJMP SUCCESS

ERROR: SJMP ERROR

END