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http:// proglit.com /. the c language. SA. BY. 1972 by Ken Thompson and Dennis Ritchie. developed concurrently with Unix C++ and Objective-C in 1980’s ANSI C89, C90, and C99 GCC (Gnu Compiler Collection) MSVC (Microsoft Visual C++). http:// proglit.com /. imperative/procedural

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http://proglit.com/


the c

language


SA

BY


1972 by Ken Thompson and Dennis Ritchie


developed concurrently with Unix

C++ and Objective-C in 1980’s

ANSI C89, C90, and C99

GCC (Gnu Compiler Collection)

MSVC (Microsoft Visual C++)


http://proglit.com/


  • imperative/procedural

  • statically typed

  • weakly typed


control of memory

explicitly manipulate individual bytes

“portable assembly”

compact data

manual allocation


(how functions are called in machine code)

calling convention

assembly from C

C from assembly


systems programming

performance-sensitive code

(operating systems, device drivers)

(games, media players)


http://proglit.com/


basic data types

char1-byte signed integer

intn-byte signed integer

floatsingle-precision floating-point

doubledouble-precision floating-point


declarations

typename;

int monkey;

float zebra;


functions

returnTypename(parameters) {body}


int square(int n)

{

return n * n;

}

int cube(int n)

{

return square(n) * n;

}


char foo(int a, float b, float c)

{

}


casting

(type) expression

int x = 35;

foo((char) x);


http://proglit.com/


!0// 1

!1// 0

!0.6// 0

!3// 0

!-76.5// 0


void roger(int x)

{

if (x == 3) {

int z = 9;

foo(z);

} else {

bar(z); // z does not exist

}

ack(z); // z does not exist

}


void roger(int x)

{

int z = 9;

if (x == 3) {

foo(z);

} else {

bar(z);

}

ack(z);

}


int main()

{

printf(“Hello, world!”);

return 0;

}


http://proglit.com/


value variables

  • float a = 9.3;


pointers

(a data type representing an address)

int*foo;

double*bar;

char*ack;


reference operator

&lvalue

char c;

int*p;

p = &c; // error

inti;

int*p;

p = &i;


reference operator

&lvalue

char c;

int*p;

p = (int*) &c;

inti;

int*p;

p = &i;


dereference operator

*pointer

inti = 3;

int*p;

p = &i;

i = *p + 2;


int i;

int*p;

p = &i;

*p = 6;


http://proglit.com/


pointer arithmetic

inti;

int*p;

p = &i + 2;

i = *p;


can subtracta pointer from a pointer

can’t adda pointer to a pointer


char*p;

p = (char*) 0xB000FFFF;

char c = *p;


int*p;

p = 0;

if (p) { … } // false


pointer comparisons

  • == !=

  • > <

  • >= <=

  • !


(can violate data types)

weak typing

float f;

f = 98.6;

f = f – 2;

char*p;

p = (char*)&f + 2;

*p = 1;


http://proglit.com/


memory allocation

malloc

free


void*p;

p = malloc(5);

float*f;

f = malloc(13);

free(p);

free(f);


sizeof operator

sizeoftype

sizeof int

sizeof double

sizeof(float *)


int*p;

p = malloc(7 * sizeof(int));

*(p + 6) = 35;

free(p);


int*p;

p = malloc(7 * (sizeofint));

if (p == 0) {

… // allocation failed

} else {

… // allocation succeeded

free(p);

}


http://proglit.com/


(a stack-allocated contiguous block of memory)

array

typename[size];

float jack[8];

char jill[200];


inti[32];

char c[11];

int *p;

p = i;

*i = -6;

*(i + 1) = 8;

*(c + 7) = (char) 5;


int sum(int *arr, int n)

{

int i = 0;

int sum = 0;

while (i < n) {

sum = *(arr + i) + sum;

i = i + 1;

}

return sum;

}


int a[30];

intsumA = sum(a, 30);

  • int *b = malloc(20 * sizeof(int));

  • intsumB = sum(b, 20);


char *fred()

{

char c[30];

return c;

}


char *fred()

{

  • char*c = malloc(30 * sizeof(char));

    return c;

    }

    char*foo = fred();

    free(foo);


http://proglit.com/


strings

char*s = “abc”;

char b = *(s + 1);

int i = strlen(s);


(a programmer-defined compound data type)

structure

structtypeName{members};

structtypeName name;

instance.member


structcat{

  • char*name;

    int age;

    }; // semi-colon!

struct cat mittens;

mittens.name = “Mittens”;

mittens.age = 5;


struct cat mittens;

  • struct cat fluffy;

    mittens = fluffy;

    struct cat *p = &fluffy;

    mittens == fluffy // illegal


struct cat cats[8];

(*cats).name = “Oscar”;

(*(cats + 1)).name = “Kitty”;


struct cat *cats =

malloc(8 * (sizeofstructcat));


http://proglit.com/


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