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C_primer_plus Chapter 2 Notes

程序员文章站 2024-02-29 17:43:28
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key concepts

Computer programming is a challenging activity. It demands abstract, conceptual thinking combined with careful attention to detail. 

To a cmoputer, "almost right is still wrong".

A program is “a description you prepare of how you want the computer to behave. The computer handles the really detailed job of converting your description to the underlying machine language".

summary

Every C program must contain a function called main() b/c it is the function called when the program starts up.

A simple function consists of

A function header

An opening brace

The statements constituting the function body

A terminating, or closing, brace

Each C statement is an instruction to the computer and is marked by terminating semicolon (;)

Declaration statement creates a name for a variable and identifies the type of data to be stored in the variable.

Assignment statement assigns a value to avariable.

A function call statement causes the named function to be executed

the printf() function

syntax 语法

semantics 语义

reviewed questions

1. functions = basic modules

4. correct form as follows

# include<stdio.h>
int main(void)    /* this prints the number of weeks in a year */
{
int a = 52;

printf("There are %d weeks in a year.\n" % a);
return 0;
}

7. one possible answer

# include<stdio.h>
int main(void)    /* this prints out the required sentence */
{
int words = 3020;
int lines = 350;

printf("There are %d words and %d lines.\n" % words, lines);
return 0;
}

exercises (possible answers)

1. 

#include <stdio.h>
int main(void)
{
printf("Gustav Mahler\n");
printf("Gustav\nMahler\n");
printf("Gustav ");
printf("Mahler\n");
return 0;
}

2. skip this one

3.

#include <stdio.h>
int main()
{
	int my_age = 30;

	printf("I am %d years old, or you may say I am %d days old.\n",
	 my_age, my_age * 365);
	return 0;
}

4.

#include <stdio.h>
void jolly(void);	// this line needs a semicolon (;) in the end
void deny(void);

int main()
{
	jolly();
	jolly();
	jolly();
	deny();
	return 0;
}

void jolly(void)
{
	printf("For he's a jolly good fellow!\n");
}

void deny(void)
{
	printf("Which nobody can deny!\n");
}

5.

#include <stdio.h>
void br(void);
void ic(void);

int main()
{
	br();
	printf(", ");
	ic();
	printf("\n");
	ic();
	printf(",\n");
	br();
	return 0;
}

void br(void)
{
	printf("Brazil, Russia");
}

void ic(void)
{
	printf("India, China");
}

6.

#include <stdio.h>
int main()
{
	int twice_toes, toes_squared, toes = 10;

	twice_toes = toes * 2, toes_squared = toes * toes;
	printf("toes: %d, twice toes: %d, toes squared: %d\n", 
		toes, twice_toes, toes_squared );
	return 0;
}

7. skip this one maybe

8.

#include <stdio.h>
void one_three(void);
void two(void);

int main()
{
	printf("starting now:\n");
	one_three();
	printf("done!\n");
	return 0;
}

void one_three(void)
{
	printf("one\n");
	two();
	printf("three\n");
}

void two(void)
{
	printf("two\n");
}