Mick's ENEE150 Stuff

enee150.c

/* 
 * ASCII Table: http://www.asciitable.com/
 * 
 */

#include <stdio.h>

int main() {
        int x = 5;
        int *y = &x;
        
        printf("Location of x: %x\n", y);
        printf("Value stored at x: %d\n", *y);
        
        *y += 1;
        
        printf("New value stored at x: %d\n", *y);
  return 0;
}

#include <stdio.h>

int main() {
char a[] = "Abcdefgh";
int i = 0;

for (i=0; i <= strlen(a); i++) {
// printf("%c", a[i]);
printf("%c", *(a+i));
}

printf("\n");
}

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

int main() {
    char *abc = NULL;
    int len = 100;
    
    abc = malloc(sizeof(char) * len);
    
    // Check if memory is allocated...
    // If malloc returned NULL, this condition will become true.
    if (!abc) {
        printf("ERROR: Could not allocate memory!\n");
        return 1;
    }
    
    strcpy(abc, "Hello, world!");
    
    printf("%s\n", abc);
}

/* Good use case for realloc
 * http://www.cplusplus.com/reference/cstdlib/realloc/
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main() {
    int *numabc = NULL;
    int *numabc_tmp = NULL;
    int len = 100;
    int len2 = 200;
    int i = 0;
    
    // I want 100 integers
    
    // WRONG WAY
    // sizeof(int) = 4
    // len = 100
    // Total bytes dedicated/allocated: 100 bytes, NOT ENOUGH
    //numabc = malloc(len);
    
    // Right way
    // sizeof(int) = 4
    // len = 100
    // Total bytes dedicated/allocated: 400 bytes
    numabc = (int *) malloc(sizeof(int) * len);
    
    // Check if memory is allocated...
    // If malloc returned NULL, this condition will become true.
    if (!numabc) {
        printf("ERROR: Could not allocate memory!\n");
        return 1;
    }
    
    for (i = 0; i < len; i++) {
        printf("%d ", *(numabc + i));
    }
    
    printf("\n");
    
    *numabc = 0;
    *(numabc + 1) = 1;
    
    for (i = 0; i < len; i++) {
        *(numabc + i) = i;
    }
    
    printf("%i\n", *numabc);
    printf("%i\n", *(numabc + len - 1));
    
    numabc_tmp = (int *) realloc(numabc, sizeof(int) * len2);
    
    if (numabc_tmp != NULL) {
       numabc = numabc_tmp;
    } else {
       free (numabc);
       puts ("Error (re)allocating memory");
       exit (1);
     }
    
    for (i = 0; i < len2; i++) {
        *(numabc + i) = i;
    }
    
    printf("%i\n", *numabc);
    printf("%i\n", *(numabc + len2 - 1));
}

/* File reading */
/* fopen: http://www.cplusplus.com/reference/cstdio/fopen/ */
/* fgetc: http://www.cplusplus.com/reference/cstdio/fgetc/ */
/* fgets: http://www.cplusplus.com/reference/cstdio/fgets/ */

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

int main() {
    /* This is a pointer, but you don't need to care about that */
    FILE *file;
    char c;
    
    file = fopen("myfile.txt", "r");
    
    if (file == NULL) {
        printf("ERROR: File can't be opened!\n");
        return 1;
    }
    
    c = fgetc(file);
    while (c != EOF) {
      printf("Char: %c\n", c);
      c = fgetc(file);
    }
    
    fclose(file);
    
    return 0;
}


/* PREPROCESSOR MACRO TUTORIAL */

#include <stdio.h>

// Conditional macros are processed ONCE - right before they are compiled.

#define bla

#ifdef bla
// Do this code
#else
// Do this code instead
#endif

// This is how the code looks like if bla is defined:
    // ...stdio.h pasted here...
    DO THiS CODE

// This is how the code looks like if bla is NOT defined:
    // ...stdio.h pasted here...
    DO THiS CODE INSTEAD