C Program Design Introduction to C Programming 主講人：虞台文

C Program DesignIntroduction to C Programming

主講人：虞台文

Content Background Main Parts of C Programs 標準輸出入裝置與輸出入函式標準輸出入函式算術運算子 (Arithmetic Operators) 關係運算子 (Relation Operators) 邏輯運算子 (Logical Operators) 巨集 The #define Preprocessor


Background

C History

Developed between 1969 and 1973 along with Unix

Due mostly to Dennis Ritchie

Designed for systems programming– Operating systems

– Utility programs

– Compilers

– Filters

Evolved from B, which evolved from BCPL

The Development of the C Language

Computer Architecture

ALUALU

ControlControl

CPU

InputInput OutputOutput

MemoryMemory

InputDevice

OutputDevice


Main Parts of

C Programs

Our First C Program Hello World

Our First C Program Hello World

/* HelloWorld.cpp Our first program */

#include <iostream>using namespace std;

/* function main begins program execution */main(){

cout << "hello, world\n";}

/* HelloWorld.cpp Our first program */

#include <iostream>using namespace std;

/* function main begins program execution */main(){

cout << "hello, world\n";}

Some Common Escape Sequences

Escape sequence Description

\n Newline. Position the cursor at the beginning of the next line.

\t Horizontal tab. Move the cursor to the next tab stop.

\a Alert. Sound the system bell.

\\ Backslash. Insert a backslash character in a string.

\" Double quote. Insert a double-quote character in a string.

Editing Compiling Linking Execution


算術運算子 (Arithmetic Operators)

Arithmetic Operators

C opetration Arithmetic operator

Algebraic expression

C expression

Addition + f + 7 f + 7

Subtraction – p – c p - c

Multiplication * bm b * m

Division / / or or x

x y x yy

x / y

Remainder % r mod s r % s

Precedence of Arithmetic Operators

Operator(s) Operation(s) Order of evaluation (precedence)

( ) Parentheses

Evaluated first. If the parentheses are nested, the expression in the innermost pair is evaluated first. If there are several pairs of parentheses “on the same level” (i.e., not nested), they are evaluated left to right.

* / %

Multiplication Division

Remainder

Evaluated second. If there are several, they are evaluated left to right.

+ -

Addition Subtraction

Evaluated last. If there are several, they are evaluated left to right.

範例 : y = 2x2+3x+7// PolynormialEval.cpp

#include <cstdlib>#include <iostream>

using namespace std;

int main(int argc, char *argv[]){ int x, y;

cout << "x = "; /* prompt */ cin >> x; /* read x */

/* Evaluate y = 2x^2 + 3x + 7 */ y = 2 * x * x + 3 * x + 7;

cout << "y = 2 * " << x << " * " << x ; cout << " + 3 * " << x << " + 7 = " << y << endl;

system("PAUSE"); return EXIT_SUCCESS;}

// PolynormialEval.cpp



int main(int argc, char *argv[]){ int x, y;

cout << "x = "; /* prompt */ cin >> x; /* read x */

/* Evaluate y = 2x^2 + 3x + 7 */ y = 2 * x * x + 3 * x + 7;

cout << "y = 2 * " << x << " * " << x ; cout << " + 3 * " << x << " + 7 = " << y << endl;

system("PAUSE"); return EXIT_SUCCESS;}

y = 2 * x * x + 3 * x + 7;

範例 : y = 2x2+3x+7

y = 2 * x * x + 3 * x + 7;


關係運算子(Relation Operators)

Relation Operators in C

Standard algebraic equality operator or relational operator

C equality or relational operator

Example of C condition

Meaning of C condition

Equality operators

== x == y x is equal to y

!= x != y x is not equal to y

Relational operators

> x > y x is greater than y

< x < y x is less than y

≥ >= x >= y x is greater than or equal to y

≤ <= x <= y x is less than or equal to y

The result of a relation operation is true (nonzero) or false (zero).

Statements

Simple Statementslower = 0;

upper = 300;

step = 20;

fahr = lower;

Null Statement; // a null statement

Compound Statements (block statements){

celsius = (5.0/9.0) * (fahr-32.0);printf("%3.0f %6.1f\n", fahr, celsius);fahr = fahr + step;

}

4 simple statements

1 compound statement

If-Else Statement

if (expression)

statement1

else

statement2

If-Else Statement

if (expression)

statement1

else

statement2

expression

If expression is evaluated to true (nonzero),

statement1 is executed;

otherwise, statement2 is executed.

If expression is evaluated to true (nonzero),

statement1 is executed;

otherwise, statement2 is executed.

startstart

endend

expressionexpression

statement1statement1 statement2

statement2

true false

If-Else Statement

if (expression)

statement1

else

statement2

expressionstartstart

endend


statement1statement1 statement2

statement2

true false

option

If-Statement

if (expression)

statement


endend


statementstatement

true

false

範例 : Decision Making (I)// pass1.cpp#include <cstdlib>#include <iostream>


int main(int argc, char *argv[]){ int threshold = 75; int score; cout << "Enter your score, please\n"; cin >> score; if (score >= threshold){ cout << "Incredible, you passed with a merit\n"; }

system("PAUSE"); return 0;}

// pass1.cpp#include <cstdlib>#include <iostream>


int main(int argc, char *argv[]){ int threshold = 75; int score; cout << "Enter your score, please\n"; cin >> score; if (score >= threshold){ cout << "Incredible, you passed with a merit\n"; }

system("PAUSE"); return 0;}

範例 : Decision Making (II)// pass2.cpp#include <cstdlib>#include <iostream>


int main(int argc, char *argv[]){ int threshold = 75; int score; cout << "Enter your score, please\n"; cin >> score; if (score >= threshold){ cout << "Incredible, you passed with a merit\n"; } else{ cout << "You failed, unlucky\n"; } system("PAUSE"); return 0;}

// pass2.cpp#include <cstdlib>#include <iostream>


int main(int argc, char *argv[]){ int threshold = 75; int score; cout << "Enter your score, please\n"; cin >> score; if (score >= threshold){ cout << "Incredible, you passed with a merit\n"; } else{ cout << "You failed, unlucky\n"; } system("PAUSE"); return 0;}

While-Statement

while(expression)

statement


endendexpressionexpression

statementstatement

true

false

範例：華氏攝氏

59 ( 32)C F

範例：華氏攝氏59 ( 32)C F

範例：華氏攝氏59 ( 32)C F



/* print Fahrenheit-Celsius table for fahr = 0, 20, ..., 300 */int main(int argc, char *argv[]){ int fahr, celsius; int lower, upper, step; lower = 0; /* lower limit of temperature scale */ upper = 300; /* upper limit */ step = 20; /* step size */ fahr = lower; while (fahr <= upper) { celsius = 5 * (fahr-32) / 9; cout << fahr << "\t" << celsius << endl; fahr = fahr + step; }

system("PAUSE"); return 0; }



/* print Fahrenheit-Celsius table for fahr = 0, 20, ..., 300 */int main(int argc, char *argv[]){ int fahr, celsius; int lower, upper, step; lower = 0; /* lower limit of temperature scale */ upper = 300; /* upper limit */ step = 20; /* step size */ fahr = lower; while (fahr <= upper) { celsius = 5 * (fahr-32) / 9; cout << fahr << "\t" << celsius << endl; fahr = fahr + step; }

system("PAUSE"); return 0; }

練習1. Using

2. Redo the same task but with the starting number, ending number, and step being given by a user.

練習3. Write a C program which asks a user to input a

positive integer. The program then reports the minimum factor of that number in 2, 3, 5, 7, 11 if available. Otherwise, reports “fail to find any factor in 2, 3, 5, 7, 11.”

4. The same as above, but the program reports all factors of that number in 2, 3, 5, 7, 11.

5. The same as above, but the program reports all possible factors of that number.


邏輯運算子(Logical Operators)

Logical Operators

&& ( logical AND ) – Returns true if both conditions are true

|| ( logical OR ) – Returns true if either of its conditions are

true

! ( logical NOT, logical negation )– Reverses the truth/falsity of its condition– Unary operator, has one operand

Truth Tables expression1 expression2 expression1 && expression2

0 0 0

0 nonzero 0

nonzero 0 0

nonzero nonzero 1

expression1 expression2 expression1 || expression2

0 0 0

0 nonzero 1

nonzero 0 1

nonzero nonzero 1

expression !expression

0 1

nonzero 0

Examples

if((celsius >= 25.0) && (celsius <= 28.0))printf("It is very comfortable\n");

if((celsius >= 25.0) && (celsius <= 28.0))printf("It is very comfortable\n");

if((celsius < 20.0) || (celsius > 32.0))printf("It is bad\n");

elseprintf("It is comfortable\n");

if((celsius < 20.0) || (celsius > 32.0))printf("It is bad\n");

elseprintf("It is comfortable\n");

if(!(celsius <= 18.0))printf("It is not very cold\n");

elseprintf("It is better to take a jacket\

n");

if(!(celsius <= 18.0))printf("It is not very cold\n");

elseprintf("It is better to take a jacket\

n");

注意事項

int total, count;. . . . . . . . .if(total / count >= 60)

printf("Passed\n");else

printf("Failed\n");



printf("Failed\n");

count若為零將產生divide by zero 之exception.

注意事項int total, count;. . . . . . . . .if(total / count >= 60)


printf("Failed\n");



printf("Failed\n");

int total, count;. . . . . . . . .if(total / count >= 60 && count > 0)


printf("Failed\n");

int total, count;. . . . . . . . .if(total / count >= 60 && count > 0)


printf("Failed\n");

int total, count;. . . . . . . . .if(count > 0 && total / count >= 60)


printf("Failed\n");

int total, count;. . . . . . . . .if(count > 0 && total / count >= 60)


printf("Failed\n");

Why?

注意事項int total, count;. . . . . . . . .if(total / count >= 60)


printf("Failed\n");



printf("Failed\n");

int total, count;. . . . . . . . .if(total / count < 60 || count == 0)

printf("Failed\n");else

printf("Passed\n");

int total, count;. . . . . . . . .if(total / count < 60 || count == 0)


printf("Passed\n");

int total, count;. . . . . . . . .if(count == 0 || total / count < 60)


printf("Passed\n");

int total, count;. . . . . . . . .if(count == 0 || total / count < 60)


printf("Passed\n");

Why?

練習main(){ int x=1,y=2,z=3; int p,q; p = (x>y) && (z<y); /* False i.e. 0 */ q = (y>x) || (y>z); /* True i.e. 1 */ printf(" %d && %d = %d\n",p,q,p&&q); printf(" %d || %d = %d\n",p,q,p||q); /* Can mix "logical" values and arithmetic */ printf(" %d && %d = %d\n",x,q,x&&q); printf(" %d || %d = %d\n",p,y,p||y); /* Exercise the NOT operator */ printf(" ! %d = %d\n",p,!p); printf(" ! %d = %d\n",q,!q); /* NOT operator applied to arithmetic */ printf(" ! %d = %d\n",z,!z);}

main(){ int x=1,y=2,z=3; int p,q; p = (x>y) && (z<y); /* False i.e. 0 */ q = (y>x) || (y>z); /* True i.e. 1 */ printf(" %d && %d = %d\n",p,q,p&&q); printf(" %d || %d = %d\n",p,q,p||q); /* Can mix "logical" values and arithmetic */ printf(" %d && %d = %d\n",x,q,x&&q); printf(" %d || %d = %d\n",p,y,p||y); /* Exercise the NOT operator */ printf(" ! %d = %d\n",p,!p); printf(" ! %d = %d\n",q,!q); /* NOT operator applied to arithmetic */ printf(" ! %d = %d\n",z,!z);}

1. 預測以下程式將產生何種結果2. 實作以下程式視預測是否正確


巨集The #define Preprocessor

#define

#include <stdio.h>#define PI 3.14159main(){ double radius;

printf("Enter the radius of a circle:"); scanf("%lf", &radius);

printf("The perimeter of the circle: %lf\n", 2.0 * PI * radius);

printf("The area of the circle: %lf\n", PI * radius * radius);

}

#include <stdio.h>#define PI 3.14159main(){ double radius;

printf("Enter the radius of a circle:"); scanf("%lf", &radius);

printf("The perimeter of the circle: %lf\n", 2.0 * PI * radius);

printf("The area of the circle: %lf\n", PI * radius * radius);

}

for text substitution

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C Program Design Introduction to C Programming 主講人：虞台文