Formatted output and variable types for beginners in C
- 2020-06-03 07:47:43
- OfStack
preface
C language is the introduction language of programming, everyone wants to learn this programming language quickly, this article introduced in detail about C language formatting output and variable type related content, share for your reference and study, let's start with a detailed introduction.
Formatted output
In PHP, we usually use echo and var_dump and print_r to output debugging statements. In C language, we usually use printf to output debugging statements. However, it is a little special that you need to specify the output data type:
#include <stdio.h>
int main(){
int age = 10;
printf("I am %d years old.\n", age);
return 0;
}
If the above code, we need to specify %d to indicate that the output is an integer, we commonly used output types are:
Tables | Are |
---|---|
d | 以10进制形式输出带符号整数(正数不输出符号) |
u | 以10进制形式输出无符号整数 |
o | 以8进制形式输出无符号整数(不输出前缀0) |
x | 以106进制形式输出无符号整数(不输出前缀Ox) |
f | 以小数形式输出单、双精度实数 |
c | 输出单个字符 |
s | 输出字符串 |
Variable types
C language is a static language. When defining variables, the type needs to be specified:
include <stdio.h>
int main(int argc, char *argv[])
{
int age = 100;
float num = 2.345f;
double super_num = 56789.4532;
char initial = 'A';
char str[] = "str";
printf("age is %d.\n", age);
printf("num is %f.\n", num);
printf("super num is %f.\n", super_num);
printf("char is %c.\n", initial);
printf("str is %s.\n", str);
return 0;
}
In addition to the basic types above, you can also define arrays:
#include <stdio.h>
int main(int argc, char *argv[])
{
int nums[] = {10, 15, 20, 14, 28};
char name[] = "Cook";
char full_name[] = {
'T', 'i', 'm','C','o','o','k','\0'
};
printf("The first num is %d, the 2nd %d.\n",areas[0], areas[1]);
printf("name=\"%s\" and full_name=\"%s\"\n",name, full_name);
return 0;
}
In C, a string is a one-byte array that ends with '\0' :
#include <stdio.h>
int main(int argc, char *argv[])
{
int nums[4] = {0};
char name[4] = {'a'};
printf("nums: %d %d %d %d\n",nums[0], nums[1],nums[2], nums[3]);
printf("name each: %c %c %c %c\n",name[0], name[1],name[2], name[3]);
printf("name: %s\n", name);
return 0;
}
Output results:
nums: 0 0 0 0
name each: a
name: a
As you can see, if an integer array is not assigned, the default value is 0, and the character array is empty. Moreover, the character array can be output directly as a string.
As for Boolean types, in C language, there is no Boolean type in the real sense, but is represented by 1 integer. Table 0 false, 1 denotes true
Data type size
The size of data type is very common in C language, we can use sizeof to detect 1 length, he returns 1 long unsigned int type, so to format the output with %ld:
#include <stdio.h>
int main(){
printf("The size of short: %ld\n", sizeof(short));
printf("The size of int: %ld\n", sizeof(int));
printf("The size of float: %ld\n",sizeof(float));
printf("The size of double: %ld\n", sizeof(double));
printf("The size of char: %ld\n", sizeof(char));
}
The operation results are as follows (64-bit machine) :
The size of short: 2
The size of int: 4
The size of float: 4
The size of double: 8
The size of char: 1
conclusion