C Language Learning 1

First, knowledge of C language

1.1The origin of C language

In 1972, Bell Labs Dennis, Ricky and Ken, Thompson the C language when developing the UNIX operating system, however, C was not entirely a whim of Ricky, he was designed on a B-language basis, and the origin of B was another story, The purpose of C language design is to use it as a programming tool for programmers, so its main goal is to become a useful language.

advantages and disadvantages of 1.2 C language

Advantages:

1. Design features: C language programming easier to understand, more reliable.

2. High efficiency: C program is more compact, and the speed of operation is fast

3. Portability: In a system C program slightly modified, or do not modify it can be run in other systems.

4. Strong flexibility: Many compilers and interpreters are written in C (FORTRAN, Perl, Python, basiac ...). ）。

5. For programmers: C language is designed to meet the needs of programmers, programmers can access the hardware through C, manipulating in-memory bits

Cons:the C language uses pointers, while programming errors involving pointers are often difficult to detect.

Ii. Overview of the C language2.1 Simple C program examples

1#include <stdio.h>2 3 voidMain ()4 {5     intnum;6num =1;7 8printf"I-a simple");9printf"coputer.\n");Tenprintf"My favorite number is%d because it is the first number\n"); One}

The results of the operation are as follows:

Note : How do I comment?

Single-line Comment://

Multiline Comment:/* Comment content */

2.2 variable naming

can be named with lowercase letters, uppercase letters, numbers, and underscores (_), and the first character of a name must be a letter or an underscore cannot be a number

2.3 Further use of C

1#include <stdio.h>2 3 voidMain ()4 {5     intfeet, fathoms;6 7Fathoms =2;8Feet =6*fathoms;9printf"there is%d feet in%d fathoms!\n", feet, fathoms);Tenprintf"Yes, I said%d feet!\n", feet); One}

The results of the operation are as follows:

iii. data and C3.1 Program Examples

1#include <stdio.h>2 3 voidMain ()4 {5     floatweight;6     floatvalue;7 8printf"is worth your weight in platinum?\n");9printf"Let ' s check it out.\n");Tenprintf"Please enter your weight in pounds:"); Onescanf"%f",&weight); AValue =1700.0* Weight *14.5833; -printf"Your weight in platinum is worth $%.2f.\n", value); -printf"You are easily worth that! If Platinum Prices drop,\n"); theprintf"eat to maintain your value.\n"); -}

Operation Result:

C Language Learning 1