C - sequential structure

1、 Assignment statement

• Add A semicolon This is the assignment statement .

2、 Data output

• Output the characters as they are

• Specify width output ： If the length is not enough, fill in the space to the left

• %m.nf： m— Represents the total length of data ,n For decimal places ,n For decimal places

  1. Actual length >n（ rounding ）
  2. Actual length <n（ Zero on the right ）

  int a=234;
  printf("a=%4d\n",a);
  printf("a=%2d\n",a);
   Output results ：
   234
  234
  
  float f=24.3567;
  printf("f=%7.2f\n",f);
  printf("f=%10.5f\n",f);
   Output results ：
    24.36
    24.35670
  
  

• The number of output items is greater than the number of output formats , Redundant items are not output

• The maximum value of the integer data range +1 Get the smallest range value , The minimum value of the range -1 Get the maximum value of the range

3、 Data input

& Address fetch Operator
Spacer There is no limit to the quantity , also It can be mixed up
If there is no other character separator for integer data input , Separate with spaces or carriage returns
The input item must be the address of the variable

• example 1：

  int a,b,c;
  scanf("%d%d%d",&a,&b,&c);
  printf("%d,%d,%d\n",a,b,c);
   Here we are a assignment 1,b assignment 2,c assignment 3, be 
   Input writing ：1 2 3
   Output results ：1,2,3
  

• example 2： Specify the width of the input data

  int a,b,c;
  scanf("%2d%3d%4d",&a,&b,&c);
  printf("%d,%d,%d\n",a,b,c);
   Input from keyboard ：1234567890
   Output results ：12,345,6789
  

• example 3： Real data input , When inputting real data , Cannot specify decimal digit

  float f;
  scanf("%7.2f",&f);	// Error can only specify width , You cannot specify the number of decimal places 
  

• example 4： Character input and output ,char Type accepts only one character ,%c There must be no blank space before

  char c1,c2;
  scanf("%c%c",&c1,&c2)
  printf("%c,%c\n",c1,c2);
   Now to c1 The assignment character A,c2 The assignment character B
   Input ：AB
   Output ：A,B
  

• Character input function ： getchar()

• Character output function ：putchar(ch)

4、 Compound statements and empty statements

4.1、 Compound statement

• form ：{ }

  {
        a=2;b=3;c=a+b;}
  

4.2、 Empty statement

• form ：;

5、 Program instance

• Enter two integers a and b, Exchange its value and output

• example 1：

  int a,b,t;
  scanf("%d%d",&a,&b);
  t=a;
  a=b;
  b=t;
  printf("%d,%d\n",a,b);
  

• example 2：

  int a,b;
  scanf("%d%d",&a,&b);
  a=a+b;
  b=a-b;
  a=a-b;
  printf("%d,%d\n",a,b);