C言語基礎学習——1日目(タイプ+オペレータ)

00main.c

int main(void)
{
    return 0;
}


      main         ,   C        main  ,            
   int           ,    void           
main                              

    : Ubuntu 12.04 gcc version 4.6.3
gcc -c main.c       -->      C   ,          : main.o
gcc main.o -o main  -->          ,              main(          a.out)

gcc main.c          -->                  a.out

C       :
hello.c   
    1. gcc -E hello.c -o hello.i == gcc -E hello.c > hello.i  (           hello.i)
       ,       cpp
    2. gcc -S hello.c -o hello.s == gcc -S hello.i -o hello.s (       hello.s)
      ,      cc1
    3. gcc -c hello.c -o hello.o == gcc -c hello.s -o hello.o (       hello.o)
      ,      as
    4. gcc hello.c -o hello      == gcc hello.o -o hello      (        hello)
      ,      ld

01hello_world.c

#include 

int main(void)
{
    printf("hello world!
");

    return 0;
}


        stdio.h                  ,
stdio.h                , printf      .

printf C              ,      printf        ,
printf        ,         .

    :
hello world!

02basic_type.c

#include 

int main(void)
{
    char ch = 0;
    short sh = 0;
    int i = 0;
    long l = 0;
    long long ll = 0;
    float f = 0.0;
    double d = 0.0;
    long double ld = 0.0;

    printf("sizeof char:       %u
", sizeof(ch));
    printf("sizeof short:      %u
", sizeof(sh));
    printf("sizeof int:        %u
", sizeof(i));
    printf("sizeof long:       %u
", sizeof(l));
    printf("sizeof long long:  %u
", sizeof(ll));
    printf("sizeof float:      %u
", sizeof(f));
    printf("sizeof double:     %u
", sizeof(d));
    printf("sizeof long double:%u
", sizeof(ld));

    return 0;
}


     (    signed unsigned)
         char, short, int, long, long long
         float, double, long double
          
            /      

sizeof     
sizeof(type)  -->        
sizeof var    -->     ,      

    ：
sizeof char:       1
sizeof short:      2
sizeof int:        4
sizeof long:       4
sizeof long long:  8
sizeof float:      4
sizeof double:     8
sizeof long double:12

03literal.c

#include 

int main(void)
{
    int a = 97;
    char ch = 'a';
    double d = 3.14e2;
    double d2 = -3.14e-2;

    printf("ch = %c
", ch);
    printf("ch = %d
", ch);
    printf("a  = %d
", a);
    printf("a  = %#o
", a);    //        , 0  
    printf("a  = %#x
", a);    //         , 0x  

    printf("d  = %lf
", d);
    printf("d2 = %lf
", d2);
    printf("d2 = %8.3lf
", d2);
    printf("d2 = %-8.3lf
", d2);
    printf("d2 = %e
", d2);

    return 0;
}


    (   : U, L):
    decimal: 3, -4, 123
    hex: 0x1a, -0x1f
    octal: 076, -025
    (   double  ):
    3.14
    3.14e2
    3.14e-2
    -3.14e-2
    : 'a', 'b', 'c'
     : "asdfg"

    :
ch = a
ch = 97
a  = 97
a  = 0141
a  = 0x61
d  = 314.000000
d2 = -0.031400
d2 =   -0.031
d2 = -0.031
d2 = -3.140000e-02

04scanf.c

#include 

int main(void)
{
    int a = 0, b = 3;

    printf("input two intergers: ");

    // &       ,      a   ,    scanf
    scanf("%d %d", &a, &b);

    printf("your inputed: a = %d, b = %d
", a, b);

    return 0;
}


    :
input two intergers: 22 44
your inputed: a = 22, b = 44

05arithmetic_operator.c

#include 

int main(void)
{
    double x, y, z;
    double ret;

    printf("input x, y, z: ");
    scanf("%lf %lf %lf", &x, &y, &z);

    ret = 3*x + 4*y - 5*z;

    printf("3x + 4y - 5z = %lf
", ret);

    int r = 10 % 3;
    printf("remainder = %d
", r);

    r = 10 / 3;
    printf("quotient = %d
", r);

    printf("r++ = %d
", r++);

    printf("++r = %d
", ++r);

    printf("--r = %d
", --r);

    printf("r-- = %d
", r--);

    return 0;
}


     :
+ - * / % ++ --

    :
input x, y, z: 2.3 5.6 -3.9
3x + 4y - 5z = 48.800000
remainder = 1
quotient = 3
r++ = 3
++r = 5
--r = 4
r-- = 4

06relational_operator.c

#include 

int main(void)
{
    int a = 3, b = 5;
    int ret;

    ret = a < b;
    printf("ret = %d
", ret);

    ret = a <= b;
    printf("ret = %d
", ret);

    ret = a > b;
    printf("ret = %d
", ret);

    ret = a >= b;
    printf("ret = %d
", ret);

    ret = a == b;
    printf("ret = %d
", ret);

    ret = a != b;
    printf("ret = %d
", ret);

    return 0;
}


     
< <= > >= == !=

    :
ret = 1
ret = 1
ret = 0
ret = 0
ret = 0
ret = 1

07logical_operator.c

#include 

int main(void)
{
    int a = 3, b = 5;
    int ret;

    ret = (a != b) && (a == b);
    printf("ret = %d
", ret);

    ret = (a != b) || (a == b);
    printf("ret = %d
", ret);

    ret = !(a < b);
    printf("ret = %d
", ret);

    return 0;
}


     
!   -->  logic not
&&  -->  logic and
||  -->  logic or

    :
ret = 0
ret = 1
ret = 0

08bit_operator.c

#include 

int main(void)
{
    int a = 3, b = 5;
    int ret = 0;

    ret = a & b;
    printf("ret = %d
", ret);  // 1

    ret = a | b;
    printf("ret = %d
", ret);  // 7

    //     ,    1,    0
    ret = a ^ b;
    printf("ret = %d
", ret);  // 6

    ret = ~a;                   // sum = a + ret, ret = sum - a
    printf("ret = %d
", ret);  // ret = sum - a = -1 - 3 = -4
    printf("ret = %u
", ret);  // ret = sum - a = 4294967295 - 3 = 4294967292

    //   ,    0
    a = 7;
    ret = a << 2;               //      4
    printf("ret = %d
", ret);  // 28

    unsigned int u = -1;
    printf("u = %u
", u);
    printf("u = %d
", u);

    //   
    // unsigned     ,    0
    ret = u >> 2; //    0     ,    %d      
    printf("ret = %d
", ret);

    //   
    // signed     ,        0   1
    a = -1;
    ret = a >> 2; // -1     1,     1,     32 1,    %d    -1
    printf("ret = %d
", ret);

    a = 15;
    ret = a >> 2; // 15     0,       0
    printf("ret = %d
", ret);

    return 0;
}


    :
~ :     
& :    
| :    
^ :     
<< :   ; >> :   

0 ^ 1 ^ 0 --> 1
0 ^ 1 ^ 1 --> 0

int a, b;
a ^ b ^ a ==> b //   1
a ^ b ^ b ==> a //   2
      int   ，    :
a = a ^ b; // a   b          a   
b = a ^ b; //       b = (a ^ b) ^ b,     2,       b = a,    a     b
a = a ^ b; //        b       a   ,         a = (a ^ b) ^ a,     2,       a = b,    b     a

    :
ret = 1
ret = 7
ret = 6
ret = -4
ret = 4294967292
ret = 28
u = 4294967295
u = -1
ret = 1073741823
ret = -1
ret = 3

09condition_operator.c

#include 

int main(void)
{
    int a = 3, b = 5;
    int min = 0;

    min = a < b ? a : b;
    printf("min of %d and %d is %d
", a, b, min);

    return 0;
}


     :

    :
min of 3 and 5 is 3

10comma_operator.c

#include 

int main(void)
{
    int a, b, c;
    int ret;

    ret = a = 3, b = 4, c = 5;  // ret     a   
    printf("a = %d b = %d c = %d, ret = %d
", a, b, c, ret);

    ret = (a = 3, b = 4, c = 5);// ret       c   
    printf("a = %d b = %d c = %d, ret = %d
", a, b, c, ret);

    return 0;
}


     

    :
a = 3 b = 4 c = 5, ret = 3
a = 3 b = 4 c = 5, ret = 5

11type_cast_1.c

#include 

int main(void)
{
    int a = 3;
    double b = 3.14;
    int reti = 0;
    double retd = 0.0;

    //       , b    
    reti = a + b;
    printf("reti = %d
", reti);

    //       , a    
    retd = a + b;
    printf("retd = %lf
", retd);

    //       
    retd = a + (int)b;  // b   ,       
    printf("retd = %lf
", retd);

    return 0;
}


    :
reti = 6
retd = 6.140000
retd = 6.000000

12type_cast_2.c

#include 

int main(void)
{
    unsigned char uch = -1;
    char ch = -1;
    int a = 385;    // 1_10000001
    int ret;

    // unsigned   ,  0  
    ret = uch;
    printf("ret = %d
", ret);  // 255

    // signed   ,        0     1  
    ret = ch;
    printf("ret = %d
", ret);  // -1
    printf("ret = %u
", ret);  // 4294967295

    ch = 127;
    ret = ch;
    printf("ret = %d
", ret);  // 127
    printf("ret = %u
", ret);  // 127

    printf("
");

    //   
    //    ,        .
    ch = a; // ch       10000001(  ,               ) -->     1 -->        1    --> 01111111 --> 127
    printf("ch = %d
", ch);
    printf("ch = %u
", ch); // ch     1,  1  , ch = 11111111_11111111_11111111_10000001

    printf("
");

    //   
    unsigned char uch1 = 253, uch2 = 255;
    ret = uch1 + uch2;
    printf("ret = %d
", ret);

    uch1 = 258, uch2 = 255;
    ret = uch1 + uch2;
    printf("ret = %d
", ret);

    return 0;
}


    :
ret = 255
ret = -1
ret = 4294967295
ret = 127
ret = 127

ch = -127
ch = 4294967169

ret = 508
ret = 257

exercise1.c

#include <stdio.h>

int main(void)
{
    int i = 0, j = 0;

    for(i = 1; i < 10; i++)
    {
        for(j = 1; j <= i; j++)
        {
            printf("%dx%d=%02d ", j, i, i*j);
        }
        printf("\n");
    }

    printf("\n");

    for(i = 9; i > 0; i--)
    {
        for(j = 1; j <= i; j++)
        {
            printf("%dx%d=%02d ", j, i, i*j);
        }
        printf("\n");
    }

    return 0;
}


  1:    9 x 9    

    :
1x1=01
1x2=02 2x2=04
1x3=03 2x3=06 3x3=09
1x4=04 2x4=08 3x4=12 4x4=16
1x5=05 2x5=10 3x5=15 4x5=20 5x5=25
1x6=06 2x6=12 3x6=18 4x6=24 5x6=30 6x6=36
1x7=07 2x7=14 3x7=21 4x7=28 5x7=35 6x7=42 7x7=49
1x8=08 2x8=16 3x8=24 4x8=32 5x8=40 6x8=48 7x8=56 8x8=64
1x9=09 2x9=18 3x9=27 4x9=36 5x9=45 6x9=54 7x9=63 8x9=72 9x9=81

1x9=09 2x9=18 3x9=27 4x9=36 5x9=45 6x9=54 7x9=63 8x9=72 9x9=81
1x8=08 2x8=16 3x8=24 4x8=32 5x8=40 6x8=48 7x8=56 8x8=64
1x7=07 2x7=14 3x7=21 4x7=28 5x7=35 6x7=42 7x7=49
1x6=06 2x6=12 3x6=18 4x6=24 5x6=30 6x6=36
1x5=05 2x5=10 3x5=15 4x5=20 5x5=25
1x4=04 2x4=08 3x4=12 4x4=16
1x3=03 2x3=06 3x3=09
1x2=02 2x2=04
1x1=01

exercise2.c

#include 

int main(void)
{
    int a = 58, b = 87;
    int temp = 0;

    printf("before: a = %d, b = %d
", a, b);
    temp = a;
    a = b;
    b = temp;
    printf("after:  a = %d, b = %d
", a, b);

    printf("
");

    a = 58, b = 87; //       
    printf("before: a = %d, b = %d
", a, b);
    a = a + b;
    b = a - b;
    a = a - b;
    printf("after:  a = %d, b = %d
", a, b);

    printf("
");

    a = 58, b = 87;
    printf("before: a = %d, b = %d
", a, b);
    a = a ^ b;
    b = a ^ b;
    a = a ^ b;
    printf("after:  a = %d, b = %d
", a, b);

    return 0;
}


  2:       ,       

    :
before: a = 58, b = 87
after:  a = 87, b = 58

before: a = 58, b = 87
after:  a = 87, b = 58

before: a = 58, b = 87
after:  a = 87, b = 58

exercise3.c

#include 

int main(void)
{
    unsigned int a = 0;
    int i = 0;

    printf("input the number: ");
    scanf("%u", &a);

    for(i = 31; i >= 0; i--)
    {
        (a & (1<putchar('1') : putchar('0');

        if((i != 0) && (i%8 == 0))
            putchar('_');
    }

    putchar('
');

    return 0;
}


  3:             

    :
input the number: 259
00000000_00000000_00000001_00000011

be careful:

unsigned int i = 0;
for(i = 31; i >= 0; i--)
{
    printf("infinite loop
"); //     
}

unsigned char j = 0;
for(j = 0; j <= 255; j++)
{
    printf("infinite loop
"); //   ,     
}