C Programming

String literal
```
scanf("%[^\n]%*c", &s);
```
In golang it is with the bufio library
Using the fgets function supplying the string length and the stdin as parameters along with the variable
```
 fgets(my_name2,20,stdin)
```

Size of an array of numbers¶

Initializing the array and populating it with values

int values[100];
    for (size_t i = 0; i <= 100; i++)
    {
        values[i]=i;
    }

To print out the length of the array we need to divide the size of it on the first element as the sizeof function returns the size in bytes. int = 4 bytes
```
printf("%lu\n",sizeof(values) / sizeof(values[0]));
/* sizeof(values) = 400 and sizeof(values[0] = 4 bytes)*/
```

Declaring functions before and after main function¶

In order to call a function before its definition it needs to have prototype declaration before main

#include <stdio.h>


void func_test(int a,int b); // This is the function prototype declaration

int main()
{
    func_test(5,10);
return 0;
}
// This is the definition
void func_test(int a,int b){ 
    int sum;

    printf("The Sum of a and b is %d\n",(a + b));
}

Casting and printing addresses of number and pointer¶

void square_num_ptr(int *num);
int main()
{
    int mynum = 35;
    square_num_ptr(&mynum);
return 0;
}

void square_num_ptr(int *num){
    int result = *num * *num;
    printf("Square of Number %d is %d\n",*num,result);
    printf("Result and Num addresses Result ADDR: %p num ADDR: %p\n",(void*)&result,(void*)num); /* Preferred way is to cast the address %p to (void*)*/
    printf("Result and Num addresses Result ADDR: %p num ADDR: %p\n",&result,(void*)num);
    return;

passing array pointers to functons does not retain the array's size and it decays . So we must pass the size separately to the function¶

#include <stdio.h>

void arrayList(int *array)
{
    for (int i = 0; i < sizeof(array) /  sizeof(array[1]); i++)
    {
        printf("Array Element %d = %d\n", i, array[i]);

    }
    printf("Size of the array %d\n",sizeof(array) / sizeof(array[1]));
}

int main()
{
    int *arrayPtr;
    int array[] = {1, 2, 3, 4, 5, 6};

    printf("Size of the array is %d\n", sizeof(array[1]));
    arrayList(array);
    return 0;
}

Output will be array size 2 from the function while it has size 24

Size of the array is 24
Array Element 0 = 1
Array Element 1 = 2
Size of the array 2

The correct code should be this

#include <stdio.h>

void arrayList(int *array,const int size)
{
    for (int i = 0; i < size; i++)
    {
        printf("Array Element %d = %d\n", i, array[i]);

    }

}

int main()
{
    int *arrayPtr;
    int array[] = {1, 2, 3, 4, 5, 6};

    printf("Size of the array is %d\n", sizeof(array));
    arrayList(array,sizeof(array) / sizeof(array[1]));
    return 0;
}

Output

Size of the array is 24
Array Element 0 = 1
Array Element 1 = 2
Array Element 2 = 3
Array Element 3 = 4
Array Element 4 = 5
Array Element 5 = 6

sum the digits of a 5 digit number using division modulo and regular¶

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

int main()
{
    int n, rem, sum;
    printf("Enter a Number\n");
    scanf("%d",&n);
    while (n != 0)
    {
        rem = n % 10;
        sum = sum + rem;
        n = n / 10;

    }
    printf("The sum is: %d\n",sum);
    return 0;
}

Advanced tpics¶

type def , custom types
enums
preprocessor , string concat
more on void*
static libraries and shared objects
macros
unions
function pointers
advanced pointers
variable arguments to functions ( variadic functions)
dynamic linking (dlm_open)
signals, forking and inter-process communication
threading and concurency
sockets
setjump and longjump
memory management and fragmentation
interfacing with kernel modules ( drivers and ioctls)
compiler and linker flags
advanced use of gdb
profiling and tracing tools(gprof, dtrace,strace)
memory debugging tools such as valgrind