“C Programming — /project-driven mode/” Author: Renfei (Neil Ren) Published: www.neilren.com 8 projects in total, from data input/output through pointers to file operations. All rights reserved; when reposting please credit the source and author. This site uses the Creative Commons Attribution-NonCommercial-NoDerivatives 2.5 China license
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Skill Objectives
Be able to correctly input/output data and perform simple aggregation.
Knowledge Objectives
- Understand C data types.
- Grasp the concepts of integer constants, integer variables, real constants, real variables, character constants, and character variables.
- Master input/output statements.
- Perform simple operations on data.
Project Requirements
Input the scores of 3 students, and compute the total and average. Program run requirements: Input 3 students’ scores: 79/89/90; total of the 3 students: 258.0; average of the 3 students: 86.0.
Task 1: Input/Output of Student Scores
Implementation code:
[code lang=“c”]#include<stdio.h> main() { int x,y,z; printf(“请输入3个学生的成绩”); scanf(“%d%d%d”,&x,&y,&z); printf(“输出3个学生的成绩”); printf(“x=%d,y=%d,z=%dn”,x,y,z); }[/code]
The structure of C
A C program consists of one or more files, and a file consists of one or more functions. A C program must contain exactly one function named main, and only one. Execution starts from main and ends back at main. As you can see from the code above, a C statement ends with a ”;”. But main() and #include are not statements and need no ”;”. A statement is made up of keywords, identifiers, operators, and expressions. ”{” and ”}” mark the start and end of a function’s execution, or the start and end of a block. Text after ”//” is a comment (single-line); you can also use ”/* multi-line comment */” for comments that span lines. The compiler ignores comments — they’re for humans and won’t be compiled. C is free-form: you can put several statements on one line, but it’s case-sensitive; uppercase and lowercase are different things.
Running our program with VC++ 6
Choose File → New, select the C++ Source File option under the Files tab, type the file name, and remember to add the “.c” suffix to indicate a C source file. Choose the save directory, then click OK to finish creating the file.
Type our code, click Build in the menu bar (some call it Compile — a translation issue), then choose Compile and click OK to compile it into an EXE executable. Note: after modifying the code you need to recompile. Then click Debug under Build to run our program and see the result.
Data Types
In the code, int x,y,z defines three integer variables. What other types are there in C?
- Basic types: integer, real (floating-point), character, and enumeration.
- Constructed types: array, structure, and union.
- Pointer types.
- Void type.
C data is divided into constants and variables, both of which also belong to the types above. A constant is fixed in the program — for example, numbers like 1, 2, 3, or symbols like A, B, C. A variable can change during the program; it is described by a type and a name — for example, string i makes i a character variable, which you can assign to and read from. Naming rules: start with a letter or underscore, followed by a combination of letters, digits, and underscores; case matters — a and A are two different things.
The formatted output function — printf()
printf() outputs to the screen. The general form is printf("format string"[, output list]). %d stands for a decimal integer, %f for a decimal fraction (6 digits by default), %c for a single character. Escape characters — the “n” in our code is an escape character meaning “newline”; search Google for more.
The formatted input function — scanf()
scanf() is used to read several values of arbitrary types from the keyboard. The form is scanf("format string", address list), where the address list is the variables — written as “&variable name”, e.g. &a means the address of a.