This program reads a C source code file, tokenizes it into keywords, identifiers, and special characters, and counts the lines. It also ignores redundant spaces, tabs, and new lines while processing the input
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
void keyword(char str[10]) {
// Check if the given string is a keyword or an identifier
if (strcmp("for", str) == 0 || strcmp("while", str) == 0 || strcmp("do", str) == 0 ||
strcmp("int", str) == 0 || strcmp("float", str) == 0 || strcmp("char", str) == 0 ||
strcmp("double", str) == 0 || strcmp("static", str) == 0 || strcmp("switch", str) == 0 ||
strcmp("case", str) == 0) {
printf("n%s is a keyword", str);
} else {
printf("n%s is an identifier", str);
}
}
int main() {
FILE *f1, *f2, *f3; // File pointers
char c, str[10], st1[10];
int num[100], lineno = 0, tokenvalue = 0, i = 0, j = 0, k = 0;
printf("nEnter the C program:");
f1 = fopen("input", "w"); // Open input file to write
while ((c = getchar()) != EOF) {
putc(c, f1); // Read from standard input and write to file
}
fclose(f1);
f1 = fopen("input", "r"); // Open input file to read
f2 = fopen("identifier", "w"); // Open identifier file to write
f3 = fopen("specialchar", "w"); // Open special character file to write
while ((c = getc(f1)) != EOF) {
// Check if the character is a digit
if (isdigit(c)) {
tokenvalue = c - '0'; // Convert character to integer
c = getc(f1);
while (isdigit(c)) {
tokenvalue = tokenvalue * 10 + (c - '0'); // Form the full number
c = getc(f1);
}
num[i++] = tokenvalue; // Store the number in the array
ungetc(c, f1); // Push back the character for further processing
}
// Check if the character is an alphabetic character
else if (isalpha(c)) {
putc(c, f2); // Write to identifier file
c = getc(f1);
while (isdigit(c) || isalpha(c) || c == '_' || c == '$') {
putc(c, f2); // Write continuous identifier characters
c = getc(f1);
}
putc(' ', f2); // Separate identifiers with a space
ungetc(c, f1); // Push back the character
}
// Ignore spaces and tabs
else if (c == ' ' || c == 't') {
printf(" ");
}
// Count new lines
else if (c == 'n') {
lineno++;
}
// Handle special characters
else {
putc(c, f3);
}
}
fclose(f2); // Close identifier file
fclose(f3); // Close special character file
fclose(f1); // Close input file
// Print numbers found in the program
printf("nThe numbers in the program are: ");
for (j = 0; j < i; j++) {
printf("%d ", num[j]);
}
printf("n");
// Read identifiers and classify them
f2 = fopen("identifier", "r");
k = 0;
printf("The keywords and identifiers are: ");
while ((c = getc(f2)) != EOF) {
if (c != ' ') {
str[k++] = c; // Collect identifier characters
} else {
str[k] = ' '; // Null-terminate the string
keyword(str); // Check if it's a keyword or identifier
k = 0; // Reset index for next identifier
}
}
fclose(f2); // Close identifier file
// Read special characters
f3 = fopen("specialchar", "r");
printf("nSpecial characters are: ");
while ((c = getc(f3)) != EOF) {
printf("%c", c); // Print special characters
}
printf("n");
fclose(f3); // Close special character file
// Print the total number of lines
printf("Total number of lines are: %d", lineno);
}
Explanation of the Code Components
-
Header Files:
#include <stdio.h>: Required for input and output functions.#include <stdlib.h>: Provides functions for memory allocation and other utility functions.#include <string.h>: Contains functions for string manipulation.#include <ctype.h>: Used for character classification functions (e.g.,isdigit,isalpha).
-
Keyword Function:
- This function checks whether a given string is a keyword or an identifier. It compares the string against known keywords and prints the appropriate message.
-
Main Function:
- The program starts execution in the
main()function. - File Handling: The program opens an input file for writing the user-provided C program, and later opens it for reading. It also creates two files for identifiers and special characters.
- Character Processing:
- Digits: If the character is a digit, it constructs the complete number by reading subsequent digit characters.
- Identifiers: If the character is an alphabet, it reads the entire identifier (which can include digits, underscores, and dollar signs) and writes it to the identifier file.
- Ignoring Whitespace: The program ignores spaces and tabs but counts new line characters.
- Special Characters: If the character is not a digit or letter, it writes the character to the special character file.
- After processing the input file, it reads the identifier file to classify identifiers and keywords and prints them. Finally, it reads and prints any special characters.
- The program starts execution in the
-
Final Output:
- The program prints all numbers found in the C program, lists the keywords and identifiers, shows the special characters, and counts the total lines in the input program.
Input:
Enter Program $ for termination:
{
int a[3],t1,t2;
t1=2; a[0]=1; a[1]=2; a[t1]=3;
t2=-(a[2]+t1*6)/(a[2]-t1);
if t2>5 then
print(t2);
else {
int t3;
t3=99;
t2=-25;
print(-t1+t2*t3); /* this is a comment on 2 lines */
} endif
}
(cntrl+z)
Output:
Variables : a[3] t1 t2 t3
Operator : - + * / >
Constants : 2 1 3 6 5 99 -25
Keywords : int if then else endif
Special Symbols : , ; ( ) { }
Comments : this is a comment on 2 lines
