The C Programming Language

  • Types, Operators and Expression
  • Control Flow
  • Functions and Program Structures
  • Pointers and Arrays
  • Structures
  • I/O
  • Unix Interface

Pointers and Structures are critical part of C.

My exercise solutions

2. Types, Operators and Expressions

Use strcpy to assig string.

3. Control Flow

switch, for, while, do-while, goto, break, continue

4. Functions and Program Structure

char is int type but only got 8bit, which is smaller than int.

C does not allow to define a function inside another function.

Split functions into different source code file.

There is no ; in #define

Use header files to store definitions.

static will limit the global variables inside the source code file scope. This means that internal static variables provide private, permanent storage within a single function.

register tells the compiler that the variable will be used heavily.

COnditional Inclusion is used in the pre-processor to have dynamic definition.

5. Pointer

pointers are variables.

*ptr is value the it points to, &value is the pointer (location).

Unary operators, such as ++, *, &, associate right to left.

By default C passes arguments to function by value.

The array name is like a pointer, but array name is not a variable! See example:

pa = &a[0];
pa = a;  // the name of the array is the pointer to the first element'
// a[i] => *(a+i)
// a++ is not legal, while pa++ is legal.

// char s[] and char *s is equivalent.

/* month_name: return name of n-th month */
char *month_name(int n)
{
    static char *name[] = {
        "Illegal month",
        "January", "February", "March",
        "April", "May", "June",
        "July", "August", "September",
        "October", "November", "December"
        };
    return (n < 1 || n > 12) ? name[0] : name[n];
}

int (*comp)(void *, void *);
/* comp is a pointer to a function that has two void * arguments and returns an int. */

Idiom way to push/pop for stack

*p++ = val;
val = *--p;
while (*s++ == *t++);
if (!*s) return 0;

Pointers to Pointers

Pointers to Functions

int (*comp) (void *, void *): comp is a pointer to a function accepts two args and return an int.

int *comp (): comp is a function that returns a pointer to an int.

6. Structures

A structure is a collection of one or more variables, possibly different types, grouped together under a single name.

A struct declaration defines a type. For example, struct point type.

Access member of structure.

p->x // if p is a pointer to a structure

p.x // if p is a structure

The structure operator, . and ->, together with () and [] are at the top of the precedence hierarchy and bind very tightly.

Reference:

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