It's our Compiler Design lab practice code.

checkDigitAndCalculate.cpp

#include<bits/stdc++.h>
using namespace std;

int main()
{
	int a, b;
	cin >> a >> b;
	//scanf("%d %d", &a, &b);
	if(a >= 0 && a <= 9 && b >= 0 && b <= 9){
		cout << "Sum: " << a + b << endl;
		cout << "Sub: " << a - b << endl;
		cout << "Mul: " << a * b << endl;
		if(b == 0){
			cout << "Can't divide with zero" << endl;
		}
		else{
			double res = (double)a / (double)b;
			cout << "Div: " << res << endl;
		}
	}
	else{
		cout << "Error" << endl;
	}
	
	return 0;
}

checkTwoStringSameOrNot.cpp

#include<iostream>
using namespace std;


int main()
{
    char str[100], str2[100];
    cout << "Enter first string: ";
    cin >> str;
    cout << "Enter 2nd string: ";
    cin >> str2;
    int flag;
    for(int i = 0; str1[i] != '\0'; i++){
        if(str[i] == str2[i]){
            flag = 0;
        }
        else{
            flag = 1;
            break;
        }
    }

    return 0;
    
}

countSpaceAndLength.cpp

#include<bits/stdc++.h>
using namespace std;

int main()
{
	char ch[100];
	int len;
	cout << "Enter a string: " << endl;
	//getting string input
	cin.getline(ch, sizeof(ch));
	
	//getting the length of a string
	for(len = 0; ch[len] != '\0'; len++);
	int space = 0;
	for(int i = 0; i != len; i++){
		if(ch[i] == ' '){
			space++;
		}
	}
	
	cout << "Length of strign: " << len << endl;
	cout << "Space of that string: " << space << endl;
	
	return 0;
	
}

detectComment.c

#include<stdio.h>
#include<string.h>

int main()
{
	char ch[100];
	int i =  2, j, flag = 0;
	
	printf("Enter a string to check comment or not: ");
	gets(ch);
	int len = strlen(ch);
	for(j = 0; j <= len; j++){
	
		if(ch[j] == '/'){
			if(ch[j+1] == '/'){
				printf("It's a line comment!\n");
				flag = 1;
				return;
			}
			else if(ch[j+1] == '*'){
				for(i = j+2; i <= len-1; i++){
					if(ch[i] == '*' & ch[i+1] == '/'){
						printf("It's multi-line comment!");
						flag = 1;
						return;
					}
					else{
						continue;
					}
				}
			}
			
		}
		if(ch[j] != '/'){
			flag = 0;
			continue;
		}
		else if(flag == 0){
			printf("it's not a comment\n");
		}
	}
	
}

Lexical Analysis.c

#include<stdio.h>
#include<string.h>
#include<ctype.h>

void main()
{

	char expr[100], operators[20]; //Arrays for storing expression and operator
	char variables[20][20]; // 2d array for storing variable or identifier
	int constants[20], ascii[100]={0}; //for storing constants, ascii values of expression
	int cnt , i, number = 0; //cnt to store string length
	int j = -1, k = -1, l= -1 ,n = 0; //counters for filling arrays
	int pr[10] = {0}, m = 0; //counters for printing identifier arrays

	printf("\n/t/tLEXICAL ANALYZER\n\n");

	printf("Enter the String\n\n"); // Accepts expression from user
	scanf ("%[^\n]%*c", expr); // "%[^\n]%*c" allows user to include spaces in entered string

	cnt = strlen(expr);
	printf("\nString length is: %d\n", cnt); //(OPTIONAL)To display string length

	for (i = 0; i < cnt; ++i) //Loop to store ascii values in array ascii
	{
		ascii[i] = (int)expr[i];
	}
	
	for(i=0;i<cnt;++i)
	
	{
	
		if( isdigit(expr[i]) ) // Condition for current element to be digit
		{
			while(isdigit(expr[i])) //Run loop until successive elements are digits
			{
				number = 10 * number + ascii[i] -'0'; // Needed to convert for eg. '3' '4' to 34
				i++;
			}
			j++;
			constants[j] = number;
			number = 0;
		}
	
		if( isalpha(expr[i]) ) //Condition for current element to be a variable
		{
			while( isalpha(expr[i]) || isdigit(expr[i]) || expr[i] == '_' ) //Run loop till next element is a letter or digit.
			{
				k++;
				variables[m][k] = expr[i];
				i++;
			}
			m++;
			pr[n] = k;
			n++;
			k = -1;
		}
	
		if(expr[i] =='+' || expr[i] =='-' || expr[i] == '/' || expr[i] == '*' || expr[i] =='=' || expr[i] == '^') // Conditions to check for operators
		{
			l++;
			operators[l]= expr[i];
		}	
	
	}
	
	//——————–Printing the Literals——————————-//
	printf("\nThe literals are: \n\n");
	for(i=0;i<=j;i++)
	{
		printf("\tlit%d\t%d \n",i+1,constants[i]);
	}
	
	//——————–Printing the Operators——————————-//
	printf("\nThe operators are: \n\n");
	for(i=0;i<=l;i++)
	{
		printf("\top%d\t%c\n",i+1,operators[i]);
	}
	
	//——————–Printing the Varibles——————————-//
	printf("\nThe variables are: \n\n");
	for(i=0;i<m;i++)
	{
		printf("\n\tid%d\t",i+1);
		for(j=0;j<=pr[i];j++)
		{
			printf("%c",variables[i][j]);
		}
		
	}
}

Problem Solve from Compiler Design Lab

My practice work that i'm solving using c or cpp or java though i'm not uploading every code here. :p

StringToASCII.c

#include<stdio.h>
#include<string.h>
int main()
{
	char ch[100];
	scanf("%[^\n]%*c", ch);
	int i = 0;
	while(i < strlen(ch)){
		printf("%c = %d\n", ch[i], ch[i]);
		i++;
	}
}