Open ended experiment

Objective of One-Pass Macro Assembler:

The one-pass macro assembler processes source code in a single pass to directly generate the final object code. Key tasks include:

1. Reading Source Code: Processes assembly instructions and macro definitions line by line.

2. Expanding Macros: Replaces macro calls with their expanded bodies.

3. Handling Labels and Directives: Resolves labels and processes directives like START, END, and ORG.

4. Building Symbol Table: Stores labels with corresponding addresses or values.

5. Managing Macros: Uses tables (MNT and MDT) to store and expand macros.

6. Generating Object Code: Directly produces final machine-level code.

Key Data Structures:

1. Symbol Table: Stores labels and addresses.

2. Macro Name Table (MNT): Stores macro names and pointers to their definitions.

3. Macro Definition Table (MDT): Stores macro bodies.

4. Argument List Array (ALA): Manages macro arguments during expansion.

#include<stdio.h>

#include<stdlib.h>

#include<string.h>

int main() {

    FILE *fp1, *mdt, *mnt, *exp;

    int MDTC = 0, MNTC = 0, i, l, k;

    char c, st[20], ALA[5];

    fp1 = fopen("INPUT_CODE.txt", "r");

    if (fp1 == NULL) {

        printf("Cannot open file Input_code\n");

        exit(0);

    }

    mdt = fopen("MDT.txt", "w");

    if (mdt == NULL) {

        printf("Cannot open file MDT\n");

        exit(0);

    }

    mnt = fopen("MNT.txt", "w");

    if (mnt == NULL) {

        printf("Cannot open file MNT\n");

        exit(0);

    }

    exp = fopen("EXPAND.txt", "w"); // Intermediate file before macro expansion

    if (exp == NULL) {

        printf("Cannot open file EXPAND\n");

        exit(0);

    }

    // Beginning of Pass 1

    do {

        fgets(st, 20, fp1); // Read one source card at a time

        if (strcmp(st, "MACRO\n") == 0) { // Check if it's a MACRO pseudo-op

            fgets(st, 20, fp1); // Read the macro name and arguments

            MNTC++;

            fprintf(mnt, "%d %s %d\n", MNTC, strtok(st, "\n"), ++MDTC); // Store in MNT

            fprintf(mdt, "%d %s", MDTC, st); // Add macro name and arguments to MDT

            i = 0, l = 0;

            // Set up ALA

            while (st[i] != '\0') {

                if (st[i] == '&') {

                    ALA[l++] = st[i + 1];

                }

                i++;

            }

            do {

                fgets(st, 20, fp1); // Read macro body

                i = 0;

                MDTC++;

                while (st[i] != '\0') { // Replace formal arguments with index notation

                    if (st[i] == '&') {

                        st[i] = '#';

                        for (k = 0; k < l; k++) {

                            if (st[i + 1] == ALA[k]) {

                                st[i + 1] = k + '0';

                            }

                        }

                    }

                    i++;

                }

                fprintf(mdt, "%d %s", MDTC, st); // Add to MDT

            } while (strcmp(st, "MEND\n") != 0); // Stop at MEND

        } else {

            fputs(st, exp); // Copy source code to EXPAND file

            if (strcmp(st, "END") == 0) {

                printf("Pass 1 complete!!\n");

                fclose(fp1);

                fclose(mdt);

                fclose(mnt);

                fclose(exp);

                return 0;

            }

        }

    } while (1);

}

START

L 1,X

ST 1,Y

MACRO

FUN &M,&N,&A

L 1,&M

A 3,&N

ST 3,&A

MEND

LINE 1

MACRO

HELLO &E,&F

L 2,&F

ST 2,&E

MEND

M 1,D5

N 2,D4

FUN P,R,P

L 1,K

HELLO S,T

FUN X,Y,Z

ST 1,K

END