Embedded Files
Introduction:-
Introduction:-
The SIC (Simplified Instructional Computer) and its extended version SIC/XE are educational computer architectures used to teach assembly language programming. SIC/XE adds complexity with more advanced instructions and flexible memory addressing. It uses a two-pass assembler process to translate assembly code into machine code.
Problem Description
Problem Description
Pass 1:
Build the Symbol Table with addresses for labels.
Generate an Intermediate File with instructions and addresses.
Manage control sections (CSECT), external definitions (EXTDEF), and references (EXTREF).
Algorithm:-
Algorithm:-
Begin
read first input line
if OPCODE = ‘START’ then begin
save #[Operand] as starting addr
initialize LOCCTR to starting address
write line to intermediate file
read next line
end( if START)
Else
initialize LOCCTR to 0
While OPCODE != ‘END’ do
Begin
if this is not a comment line then
Begin
if there is a symbol in the LABEL field then
Begin
search SYMTAB for LABEL
if found then
set error flag (duplicate symbol)
Else
(if symbol)
search OPTAB for OPCODE
if found then
add 3 (instr length) to LOCCTR
else if OPCODE = ‘WORD’ then
add 3 to LOCCTR
else if OPCODE = ‘RESW’ then
add 3 * #[OPERAND] to LOCCTR
else if OPCODE = ‘RESB’ then
add #[OPERAND] to LOCCTR
else if OPCODE = ‘BYTE’ then
begin
find length of constant in bytes
add length to LOCCTR
end
else
set error flag (invalid operation code)
end (if not a comment)
write line to intermediate file
read next input line
end { while not END}
write last line to intermediate file
Save (LOCCTR – starting address) as program length
End {pass 1}
Program:-
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
// Function prototypes
void passOne(char label[10], char opcode[10], char operand[10], char code[10], char mnemonic[3]);
void display();
int main() {
// for reading from input
char label[10], opcode[10], operand[10];
// for reading from optab
char code[10], mnemonic[3];
// Call pass1 function
passOne(label, opcode, operand, code, mnemonic);
return 0;
}
void passOne(char label[10], char opcode[10], char operand[10], char code[10], char mnemonic[3]) {
int locctr = 0, start = 0, length = 0;
char controlSection[10];
FILE *fp1, *fp2, *fp3, *fp4, *fp5; // File pointers for input, optab, symtab, intermediate file, and csect table
// Open files
fp1 = fopen("input.txt", "r"); // Input file
fp2 = fopen("optab.txt", "r"); // Optab file
fp3 = fopen("symtab.txt", "w"); // Symbol table
fp4 = fopen("intermediate.txt", "w");// Intermediate file
fp5 = fopen("csect_table.txt", "w"); // Control section table
if (!fp1 || !fp2 || !fp3 || !fp4 || !fp5) {
printf("Error opening files.\n");
exit(1);
}
// Read the first line of the input file
fscanf(fp1, "%s\t%s\t%s", label, opcode, operand);
strcpy(controlSection, label);
if (strcmp(opcode, "START") == 0) {
start = atoi(operand);
locctr = start;
fprintf(fp4, "%s\t%s\t%s\t%s\n", controlSection, label, opcode, operand);
fprintf(fp5, "%s\t%04X\t", controlSection, locctr); // Add control section name and start address
fscanf(fp1, "%s\t%s\t%s", label, opcode, operand);
}
int sectionLength = 0;
// Process the input file until END is encountered
while (1) {
// If the opcode is CSECT, update control section
if (strcmp(opcode, "CSECT") == 0) {
fprintf(fp5, "%04X\n", sectionLength); // Update previous control section length
fprintf(fp4, "%04X\t%s\t%s\t%s\n", locctr, label, opcode, operand);
locctr = 0;
sectionLength = 0;
strcpy(controlSection, label);
fprintf(fp5, "%s\t%04X\t", controlSection, locctr); // Add new control section
fscanf(fp1, "%s\t%s\t%s", label, opcode, operand);
continue;
}
// Write the intermediate file
fprintf(fp4, "%04X\t%s\t%s\t%s\n", locctr, label, opcode, operand);
// Write to symbol table if there is a label
if (strcmp(label, "**") != 0) {
fprintf(fp3, "%s\t%04X\n", label, locctr);
}
// Search for the opcode in the optab
rewind(fp2); // Reset the optab file pointer
int found = 0;
fscanf(fp2, "%s\t%s", code, mnemonic);
while (!feof(fp2)) {
if (strcmp(opcode, code) == 0) {
locctr += 3; // Increment location counter for valid opcodes
found = 1;
break;
}
fscanf(fp2, "%s\t%s", code, mnemonic);
}
// Handle pseudo-operations
if (!found) {
if (strcmp(opcode, "WORD") == 0) {
locctr += 3;
} else if (strcmp(opcode, "RESW") == 0) {
locctr += 3 * atoi(operand);
} else if (strcmp(opcode, "BYTE") == 0) {
if (operand[0] == 'C') {
locctr += strlen(operand) - 3; // Count characters in the constant
} else if (operand[0] == 'X') {
locctr += (strlen(operand) - 3) / 2; // Count bytes in the hexadecimal constant
}
} else if (strcmp(opcode, "RESB") == 0) {
locctr += atoi(operand);
}
}
// Break the loop when END is encountered
if (strcmp(opcode, "END") == 0) {
fprintf(fp4, "%04X\t%s\t%s\t%s\n", locctr, label, opcode, operand);
sectionLength = locctr;
fprintf(fp5, "%04X\n", sectionLength); // Finalize the current control section
break;
}
// Read the next line from the input file
fscanf(fp1, "%s\t%s\t%s", label, opcode, operand);
}
// Close all files
fclose(fp1);
fclose(fp2);
fclose(fp3);
fclose(fp4);
fclose(fp5);
// Display results
display();
// Calculate total length of the program
length = locctr - start;
printf("\nThe total length of the program is: %d\n", length);
}
void display() {
char str;
FILE *fp1, *fp2, *fp3, *fp4;
// Display Input File
printf("\nThe contents of the Input File:\n");
fp1 = fopen("input.txt", "r");
str = fgetc(fp1);
while (str != EOF) {
putchar(str);
str = fgetc(fp1);
}
fclose(fp1);
// Display Intermediate File
printf("\n\nThe contents of the Intermediate File:\n");
fp2 = fopen("intermediate.txt", "r");
str = fgetc(fp2);
while (str != EOF) {
putchar(str);
str = fgetc(fp2);
}
fclose(fp2);
// Display Symbol Table
printf("\n\nThe contents of the Symbol Table:\n");
fp3 = fopen("symtab.txt", "r");
str = fgetc(fp3);
while (str != EOF) {
putchar(str);
str = fgetc(fp3);
}
fclose(fp3);
// Display Control Section Table
printf("\n\nThe contents of the Control Section Table:\n");
fp4 = fopen("csect_table.txt", "r");
str = fgetc(fp4);
while (str != EOF) {
putchar(str);
str = fgetc(fp4);
}
fclose(fp4);
}
Input:-
Input:-
COPY START 0
EXTDEF BUFFER,BUFEND,LENGTH
FIRST EXTREF RDREC,WRREC
STL RETADR
CLOOP +JSUB RDREC
LDA LENGTH
COMP #0
JEQ ENDFIL
+JSUB WRREC
J CLOOP
ENDFIL LDA =C'EOF'
STA BUFFER
LDA #3
STA LENGTH
J @RETADR
RETADR RESW 1
LENGTH RESW 1
BUFFER RESB 4096
BUFEND EQU *
END FIRST
RDREC CSECT
EXTREF BUFFER,LENGTH,BUFEND
CLEAR X
CLEAR A
CLEAR S
LDT MAXLEN
RLOOP TD INPUT
JEQ RLOOP
RD INPUT
COMPR A,S
JEQ EXIT
+STCH BUFFER,X
TIXR T
JLT RLOOP
EXIT +STX LENGTH
RSUB
INPUT BYTE X'F1'
MAXLEN WORD BUFEND-BUFFER
WRREC CSECT
EXTREF LENGTH,BUFFER
CLEAR X
LDT LENGTH
WLOOP TD WOUTPUT
JEQ WLOOP
+LDCH BUFFER,X
WD WOUTPUT
TIXR T
JLT WLOOP
RSUB
WOUTPUT BYTE X'05'
END FIRST
Output:-
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