C concepts

LIBRARIES

#include <stdio.h> : standard input - output , printf , stdin , stdout

#include <string> : For string operations string a = “this is a string”

#include <stdlib.h> : (https://www.tutorialspoint.com/c_standard_library/stdlib_h.htm) standard libraries , that contains functions, size_t , free , allocate , malloc , realloc , exit , rand , srand , abort , exit , rand , RAND_MAX, EXIT_SUCCESS , EXIT_FAILURE

#include <time.h> : time() , use

cos(double) , sin(double) , tan(double) , sqrt(double) , exp(double) .. : They all accept double’s values

cosf(float), sinf(float) , tanf(float) , sqrtf(float) , expf(float) .. : They all accept float values

PRINT STATEMENTS

printf("The integer values is %d\n", integer_value);
printf("The float value is %f\n", float_value);
printf("The double value is %lf\n", double_value);
printf("The string value is %s\n", string_value);
printf("The character value is %c\n", character_value);

C-UTILS

STRUCT

struct DataStrucuture{
    int age;
    string name;
    bool gender; 
} 

MACROS

Macros in C are defined using the #define preprocessor directive. They allow you to create symbolic constants or functions that are replaced by their corresponding values or expressions during preprocessing. Defines a constant value or a function that can be used multiple times

#define PI 3.141592653589793238462643383279
#define MAX(a, b) ((a) > (b) ? (a) : (b))
#define NUM_TRAINING_EXAMPLES sizeof(training_examples) / sizeof(training_examples[0])

C LANG. COMPILATION AND LINKING

This is a bit interesting part .. and the core of C lang ..

libm : math library, used for advanced mathematical functions that provides mathematical functions like expf, sin, cos etc Written in C and some parts in assembly lang

Compilation : Translates your C code into machine code for individual parts (produces .o object files). Linking: Combines all the object files and libraries (like libm) into a final executable program.

The header files tells that compiler about declaration of these function but doesnt not include there actual code ..

Linking tells the implementation of those functions

gcc gates.c -o gates -lm : It does both compilation and linking The compilation part, gcc gates.c -o gates The linking part, ` -lm`

First gets compiled then we do the linking so that it actually runs ..

Data Types in C

Basic Types

• int
• float
• double
• char
• void

Modifier Types

• short
• long
• long long
• unsigned int
• unsigned char
• unsigned short
• unsigned long
• unsigned long long

Boolean Type

• _Bool (introduced in C99)

Complex Numbers

• _Complex (introduced in C99)
• _Imaginary (introduced in C99)

ARRAYS AND MATRICES

1D ARRAY

dtype array_name[size] = {value1, value2, value3, ...}

ex:
int arr[5] = {1, 2, 3, 4, 5};
float arr[5] = {1.1, 2.2, 3.3, 4.4, 5.5};
bool arr[5] = {true, false, true, false, true};

MATRIX

STATIC DECLARATION

dtype array_name[size1][size2] = {
    {value1, value2, value3}, 
    {value1, value2, value3}, 
    {value1, value2, value3,}
}


ex:

int arr[3][3] = {
    {1, 2, 3}, 
    {4, 5, 6}, 
    {7, 8, 9}
};


`second dimension needs to be passed (at least)`
float arr[][3] = {
    {1.1, 2.2, 3.3}, 
    {4.4, 5.5, 6.6}, 
    {7.7, 8.8, 9.9}
};


bool arr[][3] = {
    {true, false, true}, 
    {false, true, false}, 
    {true, false, true}
};

int [][2][3] = {
    {
        {1,1,1},
        {2,2,2}
    }
}

`While declaring a matrix, the first no. is not required to be explicitly mentioned rest no. needs to be mentioned`

DYNAMIC DECLARATION

FUNCTIONS

dtype function_name(input_param1, input_param2 , ){
    // perform operations 

    return xx; 
}

void function_name(int a, int b){
    int c = a + b;
    // returns nothing
}

int function_name(int a, int b){
    int c = a*b;
    return c;
}

float function_name(float a, float b){
    float c = a*b;
    return c;
}

FOR LOOP

If the type is positive and unsigned_int then we can use size_t ::

for (size_t i =0 ; i < count_size ; i++){   
        // perform operations    
}

If the type is int ::

for (int i = 0; i < count_size ; i++){
    // perform operations 
}

WHILE LOOP

while ( x < 10){
    // perform operation 
}

POINTERS AND TYPEDEF

typedef

Alias to an existing data type , doesnt create a new data type rather create a new alias for existing data type
typedef existing_name new_name

Examples: typedef unsigned long ulong; typedef struct { int x; int y;} Point typedef int* int_ptr; typedef float array_of_3_floating_number[3]

pointer

Pointer to an integer, float .. etc float* fp = 3.0f

Pointer to an float Array float* fptr = {1.0f, 2.0f, 3.0f}

Pointer to an 2D Array

float fpmat[2][3] ={
    {1.f , 2.f, 3.f}, 
    {1.f , 2.f, 3.f}
};

float* mptr[3] = fpmat; // pointer to an array of 3 floats 

BIT OF ML ALSO ADDED

DERIVATIVE IN ML

Taking the derivative of the pure function vs function with values , does that make a difference ? let’s say

USING FUNCTION WITH VALUES
dw1 = (x1*w1 + x1*eps + x2*w2) -  (x1*w1 + x2*w2) / eps ==> (x1*eps)/ eps = x1


// USING PURE FUNCTION
// dw1 = (x1*w1 + x2*w2) ==> dL/dw1 ==> x1

// Its the same thing, doesn't matter !!