Exam 1 Cheat sheet

Structure of Program

C

#include <stdio.h>
int main(){
	//body
	return 0; 
} 

C++

#include <iostream>
using namespace std;
int main(){
	//body
	return 0; 
} 

User Input

C

int main(){
int age;
printf("Enter your age: ");
scanf("%d", &age); 
printf("You are %d years old.", age); 
return 0; 
} 

C++

int main(){
int age;
cout << "Enter your age: ";
cin >> age;
cout<<"Your age is: " << age << endl;
return 0;
}

For String:

string name;
cout<<"Enter your name: ";
getline(cin, name);
cout<<"Hello,"<< name <<endl; 

Function

C

#include <stdio.h>
void greet(){
	printf("Hello!\n);
}
int main(){
	greet(); 
	return 0;
} 

C++

#include <iostream>
using namespace std;
void greet(){
	cout<<"Hello!"<<endl;
}
int main() {
	greet();
	return 0;
}

Dynamic Memory Allocation

• malloc() (C-style) – Allocates memory but does not initialize.

int main() {
    // Allocate memory for one integer
    int *ptr = (int *)malloc(sizeof(int));

    if (ptr == NULL) {
        printf("Memory allocation failed\n");
        return 1;
    }

    // Assign a value (since malloc() does not initialize)
    *ptr = 42;
    printf("Value: %d\n", *ptr);

    // Free the allocated memory
    free(ptr);

    return 0;
}

• new (C++ style) – Allocates and initializes memory.

int main() {
    // Allocate memory for one integer and initialize it to 42
    int *ptr = new int(42);

    if (!ptr) {
        cout << "Memory allocation failed" << endl;
        return 1;
    }

    cout << "Value: " << *ptr << endl;

    // Free the allocated memory
    delete ptr;

    return 0;
}

Allocating Memory for Arrays

Using malloc() (C-Style)

int *arr = (int *)malloc(5 * sizeof(int));  // Allocate an array of 5 integers

Using new[] (C++ Style)

int *arr = new int[5];  // Allocate an array of 5 integers

Understanding NULL & Safe Deletion

• If a pointer is deleted, it should be set to NULL to avoid dangling pointers:

int *p = new int(10); 
delete p; 
p = NULL;