// This program emulates a one-pass assembler for a SIC Machine. It
// requires the presence of an 'assemble.txt' file in C:\CPROGS directory
// containing a program written for said machine. It then 'assembles' the
// code present in the file and outputs the object code into 'objcod1p.txt',
// also created in the same directory.
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#define APOS 0x27
// GLOBAL VARIABLES
char OPTAB[18][7] = {"STL","JSUB","LDA","COMP","JEQ","J","STA","LDL","RSUB","LDX","TD","RD","STCH","JLT","STX","LDCH","WD","TIX"};
char OPVAL[18][3] = {"14","48","00","28","30","3C","0C","08","4C","04","E0","D8","54","38","10","50","DC","2C"};
char SYMTAB[20][10];
int SYMVAL[20], numberOfSymbols = 0;
int forwardReferences[20], nOfFR = 0, refAddress[20];
int OPTABVal, SYMTABVal;
char outputString[30];
char gotLine[50][50], OPCODE[20], OPERAND[20], LABEL[20];
int nLines = 0, programLength = 0, startAddress = 0, currentAddress = 0, progress = 0, LOCCTR, oldLOCCTR;
char currLABEL[20];
FILE *fpIN, *fpOUT;
char startAddressAsString[7] = {'0','0','0','0','\0'};
int processFile() {
char c;
int location = 0, endNow = 0;
if((fpIN = fopen("c:/cprogs/assemble.txt", "r+")) == NULL) {
printf("Error! File not found!\n" );
return(1);
}
printf("File Opened! Reading contents...\n\n"); getch();
c = getc(fpIN);
while(endNow != 1) {
if(c != '\n') {
gotLine[nLines][location] = c;
location++;
}
else {
gotLine[nLines][location] = '\0';
location = 0;
while(gotLine[nLines][location] != '\0') {
printf("%c", gotLine[nLines][location]);
location++;
}
printf("\n");
location = 0;
nLines++;
}
if((c = getc(fpIN)) == EOF) {
endNow = 1;
}
}
printf("File has ended! Contents have been stored in local array. Closing file...");
getch();
fclose(fpIN);
return(0);
}
void getCodesFromLine(int line) {
int location = 0, nWords = 1, inLoc = 0;
while(gotLine[line][location] != '\0') {
if(gotLine[line][location] == ' ') {
nWords++;
}
location++;
}
location = 0;
if(nWords > 2) {
while(gotLine[line][location] != ' ') {
LABEL[inLoc] = gotLine[line][location];
location++;
inLoc++;
}
LABEL[inLoc] = '\0';
inLoc = 0;
location++;
while(gotLine[line][location] != ' ') {
OPCODE[inLoc] = gotLine[line][location];
location++;
inLoc++;
}
OPCODE[inLoc] = '\0';
inLoc = 0;
location++;
while(gotLine[line][location] != '\0') {
OPERAND[inLoc] = gotLine[line][location];
location++;
inLoc++;
}
OPERAND[inLoc] = '\0';
}
else if(nWords > 1) {
while(gotLine[line][location] != ' '){
OPCODE[inLoc] = gotLine[line][location];
inLoc++;
location++;
}
OPCODE[inLoc] = '\0';
inLoc = 0;
location++;
while(gotLine[line][location] != '\0') {
OPERAND[inLoc] = gotLine[line][location];
inLoc++;
location++;
}
OPERAND[inLoc] = '\0';
LABEL[0] = 'N';
LABEL[1] = 'U';
LABEL[2] = 'L';
LABEL[3] = 'L';
LABEL[4] = '\0';
}
else {
while(gotLine[line][location] != ' ' && gotLine[line][location] != '\0') {
OPCODE[inLoc] = gotLine[line][location];
inLoc++;
location++;
}
OPCODE[inLoc] = '\0';
OPERAND[0] = 'N';
OPERAND[1] = 'U';
OPERAND[2] = 'L';
OPERAND[3] = 'L';
OPERAND[4] = '\0';
LABEL[0] = 'N';
LABEL[1] = 'U';
LABEL[2] = 'L';
LABEL[3] = 'L';
LABEL[4] = '\0';
}
}
int opInt() {
int b = 0, i = 0;
while(OPERAND[i] != '\0') {
b = b + OPERAND[i] - 48;
b*=10;
i++;
}
b/=10;
return(b);
}
int isDuplicateLabel() {
int i = 0;
while(i < 18) {
if(strcmp(LABEL, SYMTAB[i]) == 0)
return(1);
i++;
}
return(0);
}
int isOPERANDinSYMTAB() {
int i = 0;
while(i < numberOfSymbols) {
if(strcmp(OPERAND, SYMTAB[i]) == 0) {
SYMTABVal = SYMVAL[i];
return(1);
}
i++;
}
return(0);
}
int isOPCODEValid() {
int i = 0;
while(i < 18) {
if(strcmp(OPCODE, OPTAB[i]) == 0) {
OPTABVal = i;
return(1);
}
i++;
}
return(0);
}
void insertIntoSYMTAB(int location) {
int i = numberOfSymbols;
numberOfSymbols++;
strcpy(SYMTAB[i], LABEL);
SYMVAL[i] = location;
}
void initOutputFile() {
char output[50] = {'H','\0'}, start[8], length[8] = {'0','0','0','0','0','\0'}, endline[2] = {'\n', '\0'};
int nameLength, startLength, lengthLength;
printf("\n\nInserting header record... Name: %s", LABEL);
fpOUT = fopen("c:/cprogs/objcod1p.txt", "w+");
itoa(startAddress, start, 10);
printf("\nStarting address: %s\nProgram Length: %s\n", start, length);
nameLength = strlen(LABEL) + 1;
startLength = strlen(start) + 1;
lengthLength = strlen(length) + 1;
strcat(output, LABEL);
while(nameLength <= 7) {
output[nameLength] = ' ';
nameLength++;
}
while(startLength < 7) {
output[nameLength] = '0';
startLength++;
nameLength++;
}
output[nameLength] = '\0';
strcat(output, start);
nameLength += startLength;
while(lengthLength < 7) {
output[nameLength] = '0';
lengthLength++;
nameLength++;
}
output[nameLength] = '\0';
strcat(output, length);
nameLength += lengthLength;
output[nameLength] = '\0';
strcat(output, endline);
fputs(output, fpOUT);
}
void writeToFile(int lengthOfString) {
char output[50] = {'T','\0'}, start[8], length[3], endline[2] = {'\n', '\0'};
itoa(lengthOfString, length, 10);
currentAddress += progress;
progress = lengthOfString;
itoa(currentAddress, start, 10);
strcat(output, start);
strcat(output, length);
strcat(output, outputString);
strcat(output, endline);
fputs(output, fpOUT);
}
void writeEndRecordAndClose() {
char output[50] = {'E','0','0','\0'};
strcat(output, startAddressAsString);
fputs(output, fpOUT);
fseek(fpOUT, 15, 0);
output[0] = '\0';
itoa(programLength, output, 10);
output[4] = '\n';
output[5] = '\0';
fputs(output, fpOUT);
fclose(fpOUT);
}
void searchAndReplaceFR() {
char output[50] = {'T','\0'}, length[3] = {'0','2','\0'}, address[10], location[10];
int tempNum = nOfFR;
itoa((LOCCTR), location, 10);
location[4] = '\n';
location[5] = '\0';
//printf("\nChecking FR-s for LABEL = %s", currLABEL); getch(); // DEBUG
while(tempNum >= 0) {
getCodesFromLine(forwardReferences[tempNum]);
if(strcmp(OPERAND, currLABEL) == 0) {
itoa((refAddress[tempNum] + 1), address, 10);
strcat(output, address);
strcat(output, length);
strcat(output, location);
fputs(output, fpOUT);
output[0] = 'T';
output[1] = '\0';
}
tempNum--;
}
}
int main() {
int fileReadError = 0, currentLine = 0, digit1, digit2, digit3, digit4, inLoc, constLength, i, j, lengthOfOutputString;
char operationCode[10], operandAddress[5] = {'0','0','0','0','\0'}, tempOPERAND[20], tempString[10];
clrscr();
fileReadError = processFile();
if(fileReadError == 1) {
printf("\nPlease ensure that 'assemble.txt' is present in root of C drive.\nPress any key to exit...");
getch();
return(1);
}
//printf("\nGetting codes from line for first time..."); getch(); // DEBUG
getCodesFromLine(currentLine);
if(strcmp(OPCODE, "START") == 0) {
startAddress = opInt();
LOCCTR = startAddress;
currentAddress = startAddress;
itoa(startAddress, startAddressAsString, 10);
currentLine++;
getCodesFromLine(currentLine);
printf("\nSTART encountered. Start address is %d", startAddress); getch();
}
else
LOCCTR = 0;
initOutputFile(); // write Header record to object program & initialize first Text Record
printf("\nInitializing assembling process..."); getch();
while(strcmp(OPCODE, "END") != 0) { // While OPCODE is not 'END'
//printf("\nEvaluating new line..."); getch(); // DEBUG
if(gotLine[currentLine][0] != '.') { // If current line is not a comment line
if(strcmp(LABEL, "NULL") != 0) { // If there is a label
if(isDuplicateLabel() == 1) { // If there is a duplicate label in SYMTAB
printf("\n\nError! Duplicate Label Encountered!\nThe assembly program is invalid. Press any key to exit...");
getch();
return(1);
}
else { // If there is no duplicate
//printf("\nInserting into SYMTAB, and checking for existing forward references..."); getch(); // DEBUG
printf("\n%s - %d", LABEL, LOCCTR);
insertIntoSYMTAB(LOCCTR);
//printf("\nInsertion into SYMTAB Complete. Proceeding with SearchAndReplaceFR()..."); getch(); // DEBUG
strcpy(currLABEL, LABEL);
searchAndReplaceFR();
printf("\nForward references associated with the above symbol have been dealt with..."); getch(); // DEBUG
getCodesFromLine(currentLine);
}
}
if(isOPCODEValid() == 1) { // If OPCODE exists
//printf("\nValid OPCODE encountered..."); getch(); // DEBUG
if(strcmp(OPERAND, "NULL") != 0) { // If OPERAND is available
if(isOPERANDinSYMTAB() == 1) { // If OPERAND is in SYMTAB
itoa(SYMTABVal, operandAddress, 10); // strore SYMBOL value as Operand address
}
else {
forwardReferences[nOfFR] = currentLine;
refAddress[nOfFR] = LOCCTR;
nOfFR++;
printf("\nUndefined Symbol Encountered on Line %d!\nContinuing execution by placing a forward reference marker.", (currentLine + 1));
operandAddress[0] = '0';
operandAddress[1] = '0';
operandAddress[2] = '0';
operandAddress[3] = '0';
operandAddress[4] = '\0';
}
}
else { // Operand Address default value is '0000'
operandAddress[0] = '0';
operandAddress[1] = '0';
operandAddress[2] = '0';
operandAddress[3] = '0';
operandAddress[4] = '\0';
}
strcpy(operationCode, OPVAL[OPTABVal]); // set Operation Code
strcat(outputString, OPVAL[OPTABVal]);
strcat(outputString, operandAddress);
LOCCTR += 3;
}
else if(strcmp(OPCODE, "BYTE") == 0 || strcmp(OPCODE, "WORD") == 0) { // convert constant to object code
if(strcmp(OPCODE, "WORD") == 0) {
i = 0;
constLength = strlen(OPERAND);
while(constLength < 6) {
tempOPERAND[i] = '0';
constLength++;
i++;
}
tempOPERAND[i] = '\0';
strcat(tempOPERAND, OPERAND);
strcat(outputString, tempOPERAND);
LOCCTR += 3;
}
else {
i = 2;
j = 0;
if(OPERAND[0] == 'X') {
while(APOS != OPERAND[i]) {
tempString[j] = OPERAND[i];
j++;
i++;
}
tempString[j] = '\0';
}
else {
tempString[0] = '4';
tempString[1] = '5';
tempString[2] = '4';
tempString[3] = 'F';
tempString[4] = '4';
tempString[5] = '6';
tempString[6] = '\0';
}
strcat(outputString, tempString);
if(OPERAND[0] == 'X') {
LOCCTR++;
}
else {
LOCCTR += 3; // INCOMPLETE. This simplification is insufficient. Refer algorithm for detail.
}
}
}
else if(strcmp(OPCODE, "RESW") == 0)
LOCCTR += (3 * opInt());
else if(strcmp(OPCODE, "RESB") == 0)
LOCCTR += 1000;
else {
printf("\n\nError! Invalid Operation Code Encountered!\nThe assembly program is invalid. Press any key to exit...");
getch();
return(1);
}
}
currentLine++;
getCodesFromLine(currentLine);
if(strcmp(outputString, "000000") != 0) {
printf("\nObject Code Array: %s", outputString);
getch();
}
lengthOfOutputString = (strlen(outputString) / 2);
if(lengthOfOutputString >= 12) { // if object code will not fit into the current text record then
writeToFile(lengthOfOutputString); //write Text record to object program
outputString[0] = '\0'; //initialize new Text record
printf("\nObject Code Array has reached maximum size. Purging to file..."); getch();
}
}
programLength = LOCCTR - startAddress;
getch();
printf("\nFinished assembling code...\nPurging remainging object code to file and writing End Record..."); getch();
lengthOfOutputString = strlen(outputString); // write last Text record to object program
writeToFile(lengthOfOutputString);
currentLine = 0;
outputString[0] = '\0'; // Purge outputString
getCodesFromLine(currentLine);
writeEndRecordAndClose(); // write End record to object program
printf("\nEnd Record has been written. Press any key to exit..."); getch();
return(0);
}
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