C development

Param format: String that contains the text to be written to the stream. It can optionally contain embedded format tags that are replaced by the values specified in subsequent additional arguments and formatted as requested. Format tags prototype is %[flags][width][.precision][length]specifier (see 'printf' for tags).

Param additional aguments: Depending on the format string, the function may expect a sequence of additional arguments, each containing one value to be inserted instead of each %-tag specified in the format parameter, if any. There should be the same number of these arguments as the number of %-tags that expect a value.

Returns Total number of characters written, if successful. A negative number otherwise.

int fputc(int char, FILE *stream)

Writes a character (an unsigned char) specified by the argument char to the specified stream and advances the position indicator for the stream.

int fputs(const char str, FILE stream)

Writes a string to the specified stream up to but not including the null character.

int fscanf(FILE stream, const char format, ...)

It reads formatted input from a stream.

See fopen for an example.

int fseek(FILE *stream, long int offset, int whence)

Sets the file position of the stream to the given offset. The argument offset signifies the number of bytes to seek from the given whence position.

Param stream: Pointer to a FILE object that identifies the stream.

Param offset: Number of bytes to offset from whence.

Param whence: Position from where offset is added. It is specified by one of the following constants −

SEEK_SET Beginning of file
SEEK_CUR Current position of the file pointer
SEEK_END End of file

Returns zero if successful, or else it returns a non-zero value.

int getchar(void)

Returns the character read as an unsigned char cast to an int or EOF on end of file or error.

#include <stdio.h>

int main() {

int c,cont=0;

printf("Digite su nombre: y luego ctrl + z\n");

while (EOF != (c=getchar()))

{

switch (c)

{

case 'a':

case 'e':

case 'i':

case 'o':

case 'u':cont++;

}

printf("El numero de vocales es: %i",cont);

return 0;

}

gets

Deprecated, use fgets w/ strtok instead.

printf

int putchar(int char)

Writes a character (an unsigned char) specified by the argument char to stdout.

Param char The character to be written. This is passed as its int promotion.

Return The character written as an unsigned char cast to an int or EOF on error.

puts

int remove(const char *filename)

Deletes the given filename so that it is no longer accessible.

Param filename String containing the name of the file to be deleted.

Return On success, zero. On error, -1, and errno is set appropriately.

void rewind(FILE *stream)

Sets the file position to the beginning of the file of the given stream.

Param stream Pointer to a FILE object that identifies the stream.

scanf

For string, see also gets.

scanf("%f %f", &num1, &num2); //Read 2 floats

Functions: stdlib.h

int atoi(const char *nptr)

Skips all white-space characters at the beginning of the string, converts the subsequent characters as part of the number, and then stops when it encounters the first character that isn't a number.

Param nptr Pointer to a string to convert to an integer.

Return The integer representation of a string.

double atof(const char *nptr)

Skips all white-space characters at the beginning of the string, converts the subsequent characters as part of the number, and then stops when it encounters the first character that isn't a number.

Param nptr Pointer to a string to convert to a floating-point number (double).

Return The floating-point representation of a string.

void *calloc(size_t nitems, size_t size)

Allocates the requested memory and returns a pointer to it. The difference in malloc and calloc is that malloc does not set the memory to zero where as calloc sets allocated memory to zero.

Param nitems Number of elements to be allocated.

Param size Size of elements.

Return A pointer to the allocated memory, or NULL if the request fails.

void free(void *ptr)

Deallocates the memory previously allocated by a call to calloc, malloc, or realloc.

Param ptr Pointer to a memory block previously allocated with malloc, calloc or realloc te be deallocated.

If a null pointer is passed as argument, no action occurs

void *malloc(size_t size)

Allocates the requested memory and returns a pointer to it. Function free is used to free it.

Param size Size of the memory block, in bytes

Return A pointer to the allocated memory, or NULL if the request fails.

#include <stdio.h>

int main() {

int* array;

array = (int*)malloc(4*8);

if (array != NULL)

printf("La memoria se ha otorgado\n");

else

printf("Error al adquirir la memoria\n");

int* array;

array = (int*)malloc(sizeof(int)*8);

if (array != NULL)

printf("La memoria se ha otorgado\n");

else

printf("Error al adquirir la memoria\n");

free(array);

#define SIZE 1000000

int* myArray = (int*)malloc(sizeof(int)*SIZE);

if (myArray == NULL)

printf("Se alcanzo el limite de memoria\n");

free(myArray);

return 0;

}

int rand(void)

Returns an integer value between 0 and RAND_MAX (which it's granted to be at least 32767).

See 'srand' function for an example.

void realloc(void ptr, size_t size)

Attempts to resize the memory block pointed to by ptr that was previously allocated with a call to malloc or calloc.

Param ptr Pointer to a memory block previously allocated with malloc, calloc or realloc to be reallocated.

If this is NULL, a new block is allocated and a pointer to it is returned by the function.

Param size The new size for the memory block, in bytes. If it is 0 and ptr points to an existing block of memory, the memory block pointed by ptr is deallocated and a NULL pointer is returned.

Return A pointer to the newly allocated memory, or NULL if the request fails.

void srand(unsigned int seed)

Param seed − This is an integer value to be used as seed by the pseudo-random number generator algorithm.

#include <stdio.h>

#include <stdlib.h>

#include <time.h>

int main () {

int i, n;

time_t t;

n = 5;

/* Intializes random number generator */

srand((unsigned) time(&t));

/* Print 5 random numbers from 0 to 50 */

for( i = 0 ; i < n ; i++ ) {

printf("%d\n", rand() % 50);

}

return(0);

}

int system(const char *_Command)

system("clear"); //Clear screen (cls on Windows)

system("dir"); //SO command dir

system("PAUSE");

Functions: string.h

char strcat(char destination, const char *source)

It concatenates the destination string and the source string, and the result is stored in the destination string.

Note: The size of the destination string should be large enough to store the resultant string.

int strcmp (const char* str1, const char* str2)

0 if strings are equal

>0 if the first non-matching character in str1 is greater (in ASCII) than that of str2.

<0 if the first non-matching character in str1 is lower (in ASCII) than that of str2.

char* strcpy(char* destination, const char* source);

It copies the string pointed by source (including the null character) to the destination.

It returns the copied string.

size_t strlen(const char *str)

It takes a string as an argument and returns its length as type size_t (unsigned integer).

char a[20]="Program";

char b[20]={'P','r','o','g','r','a','m','\0'};

// using the %zu format specifier to print size_t

printf("Length of string a = %zu \n",strlen(a)); // 7

printf("Length of string b = %zu \n",strlen(b)); // 7

char strlwr(char str)

It converts a given string into lowercase.

char strrchr(const char str, int c)

It searches for the last occurrence of the character c (an unsigned char) in the string pointed to, by the argument str.

It returns a pointer to the last occurrence of character in str. If the value is not found, the function returns a null pointer.

int len;

const char str[] = "http://www.tutorialspoint.com";

const char ch = '.';

char *ret;

ret = strrchr(str, ch);

printf("String after |%c| is - |%s|\n", ch, ret);

// String after |.| is - |.com|

char strrev(char str)

It reverses the given string.

It doesn't return anything but the reversed string is stored in the same string

char strtok(char str, const char *delim)

The contents of this string 'str' are modified and broken into smaller strings (tokens).

It returns a pointer to the first token found in the string. A null pointer is returned if there are no tokens left to retrieve.

char nombre[20];

fgets(nombre, 20, stdin);

strtok(nombre, "\n"); //Removes the trailing new line typed by the user

char strupr(char str)

It converts a given string into uppercase.

Functions: time.h

time_t time(time_t *seconds)

Parameter seconds is a pointer to an object of type time_t, where the seconds value will be stored.

It returns the time since 00:00:00 UTC, January 1, 1970 (Unix timestamp) in seconds.

time_t seconds = time(NULL);

time_t seconds;

// Stores time seconds

time(&seconds);

Functions: custom

#include <stdio.h>

void Mundo(); //Declare function before using it on 'main'

int main() {

Mundo();

return 0;

}

void Mundo(){

printf("Hola Mundo\n");

}

Operators

Aritméticos

++ Preincremento int b = ++a; Postincremento int b = a++;

Relational (operators)

!= If the two operands aren't equal

Lógicos

Asignación

+= Suma y asignación. Eg: a += 3; is the same than a = a + 3;

/= Divide and assignment

%= Módulo y asignación

sizeof

Param Operand which size will be computed.

Return The amount of memory allocated, when it's used with data types.

#include <stdio.h>

int main() {

int a = 16;

printf("Size of variable a : %d

",sizeof(a));

printf("Size of int data type : %d

",sizeof(int));

printf("Size of char data type : %d

",sizeof(char));

printf("Size of float data type : %d

",sizeof(float));

printf("Size of double data type : %d

",sizeof(double));

return 0;

}

Flow control

if

Conditional.

int a,b;

a=b=3;

int c = a+b;

if (a+b == 6) {

printf("Result is %i", c);

} else if (condition2) {

// block of code to be executed if the condition1 is false and condition2 is true

} else {

// block of code to be executed if the condition1 is false and condition2 is false

}

switch

The value of the expressions in a switch-case statement must be an ordinal type i.e. integer, char, short, long, etc. Float and double are not allowed.

int day = 4;

switch (day) {

case 1:

printf("Monday");

break;

case 2:

printf("Tuesday");

break;

case 3:

printf("Wednesday");

break;

case 4:

printf("Thursday");

break;

case 5:

printf("Friday");

break;

case 6:

printf("Saturday");

break;

case 7:

printf("Sunday");

break;

}

// Outputs "Thursday" (day 4)

? ternary operator

int numero;

puts("Write a number\n");

scanf("%i, &numero);

(numero % 2 == 0) ? printf("El numero es par\n") : printf("El numero es impar\n");

for

Inline variable declaration only allowed in mode C99 or C11.

for (int i=0; i<10; i++) {

printf("* %i\n", i);

}

while

/* local variable definition */

int a = 10;

/* while loop execution */

while( a < 20 ) {

printf("value of a: %d\n", a);

a++;

}

do...while

It checks its condition at the botton of the loop; unlike for and while loops.

/* local variable definition */

int a = 10;

/* do loop execution */

do {

printf("value of a: %d\n", a);

a = a + 1;

}while( a < 20 );

Algorithms search and traversal

Traversal over table (direct access)

TBD

Traversal over sequence

TBD

Search over table (direct access)

Generic search w/ direct access. The table isn't ordered so a sequential search is performed.

#include <stdio.h>

int main() {

int a[10]={2,4,6,8,0,1,3,5,7,9};

int i, dato;

char band = 'F';

printf("Escribe un numero\n");

scanf("%i",&dato);

i=0;

while ((band == 'F') && (i < 10)){

if (a[i] == dato){

band = 'V';

}

i++;

}

if (band == 'F'){

printf("El numero no existe en la lista\n");

}else if (band == 'V'){

printf("El numero existe, en la posicion %i ",i-1);

}

return 0;

}

Search over sequence

TBD

Algorithms: order array using bubble method, and binary search it

It orders and array of integers, ascending and then it performs a binary search on it.

#include <stdio.h>

int main() {

int a[10] = {1,3,5,7,9,2,4,6,8,10};

int i,j,aux,dato,inf,sup,mitad;

char band = 'F';

//Metodo burbuja

for (i = 0; i < 10; i++){

for (j = 0; j < 10; j++){

if (a[j] > a[j+1]){

aux = a[j];

a[j] = a[j+1];

a[j+1] = aux;

}

for (i = 0; i < 10; i++){

printf("%i, ",a[i]);

}

printf("\nEscribe un numero: ");

scanf("%i",&dato);

//Busqueda Binaria

inf = 0;

sup = 10;

while (inf <= sup){

mitad = (inf+sup)/2;

if (a[mitad] == dato){

band = 'V';

break;

}

if (a[mitad] > dato){

sup = mitad;

mitad = (inf+sup)/2;

}

if (a[mitad] < dato){

inf = mitad;

mitad = (inf+sup)/2;

}

if (band == 'F'){

printf("El numero no existe\n");

}else if (band == 'V'){

printf("El numero existe en la posicion %i",mitad);

}

return 0;

}

Sample: Hello world!

#include <stdio.h>

int main(){

printf("Hola Mundo");

return 0;

}

Sample: Arrays always passed by reference

#include <stdio.h>

//* Esta Funcion Recibe un Array y lo llena

//! Nota que no se indica el numero de indices que recibira, se hace con otra variable

void llenarArray(int Array[],int dimension){

for(int i = 0; i<dimension;i++){

printf("\nDame el valor [%d] del array",i);

scanf("%d",&Array[i]);

}

int main() {

int miVector[5];

//* Solo pasamos el nombre del array y su dimension

llenarArray(miVector,5);

//! Imprimimos sus valores

//? Recuerda que por defecto el array se hace con paso de parametros por referencia

//? Esto nos permite editarlo desde otra funcion

for (int x = 0; x < 5; x++){

printf("%d",miVector[x]);

}

return 0;

}

Sample: Pointer to array

#include <stdio.h>

int main() {

//*Declaramos un array de 5 indices

int array[5] = {1,2,3,4,5};

//! Ahora un apuntador al inicio de la variable

int* apuntadorArray = &array[0];

//* Con esto podemos desplazarnos por el array sin conocer su dimension

while (*apuntadorArray != NULL){

printf("\n %d",*apuntadorArray);

apuntadorArray++; //! Se va recorriendo el array por las posiciones

}

return 0;

}