Sams Teach Yourself C in 24 Hours (74 page)

DataRead(fptr);

}

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497

/* function definition */

long PtrTell(FILE *fptr)

{

long reval;

reval = ftell(fptr);

printf(“The fptr is at %ld\n”, reval);

return reval;

}

/* function definition */

void DataRead(FILE *fptr)

{

char buff[MAX_LEN];

fgets(buff, MAX_LEN, fptr);

printf(“%s”, buff);

}

/* function definition */

int ErrorMsg(char *str)

{

printf(“Cannot open %s.\n”, str);

B

return FAIL;

}

3. On my machine, the data.bin binary file is 10 bytes. The following is one possible solution:

/* 22A03.c */

#include

enum {SUCCESS, FAIL};

void DataWrite(FILE *fout);

void DataRead(FILE *fin);

int ErrorMsg(char *str);

main(void)

{

FILE *fptr;

char filename[]= “data.bin”;

int reval = SUCCESS;

if ((fptr = fopen(filename, “wb+”)) == NULL){

reval = ErrorMsg(filename);

} else {

DataWrite(fptr);

rewind(fptr);

DataRead(fptr);

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498

Appendix B

fclose(fptr);

}

return reval;

}

/* function definition */

void DataWrite(FILE *fout)

{

double dnum;

int inum;

dnum = 123.45;

inum = 10000;

printf(“%5.2f\n”, dnum);

fwrite(&dnum, sizeof(double), 1, fout);

printf(“%d\n”, inum);

fwrite(&inum, sizeof(int), 1, fout);

}

/* function definition */

void DataRead(FILE *fin)

{

double x;

int y;

printf(“\nRead back from the binary file:\n”);

fread(&x, sizeof(double), (size_t)1, fin);

printf(“%5.2f\n”, x);

fread(&y, sizeof(int), (size_t)1, fin);

printf(“%d\n”, y);

}

/* function definition */

int ErrorMsg(char *str)

{

printf(“Cannot open %s.\n”, str);

return FAIL;

}

4. The following is one possible solution:

/* 22A04.c */

#include

enum {SUCCESS, FAIL,

MAX_NUM = 3,

STR_LEN = 23};

void DataRead(FILE *fin);

int ErrorMsg(char *str);

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499

main(void)

{

FILE *fptr;

char filename[]= “strnum.mix”;

int reval = SUCCESS;

if ((fptr = freopen(filename, “r”, stdin)) == NULL){

reval = ErrorMsg(filename);

} else {

DataRead(fptr);

fclose(fptr);

}

return reval;

}

/* function definition */

void DataRead(FILE *fin)

{

int i;

int miles;

char cities[STR_LEN];

printf(“The data read:\n”);

B

for (i=0; i

scanf(“%s%d”, cities, &miles);

printf(“%-23s %d\n”, cities, miles);

}

}

/* function definition */

int ErrorMsg(char *str)

{

printf(“Cannot open %s.\n”, str);

return FAIL;

}

Hour 23, “Compiling Programs: The C

Preprocessor”

Quiz

1. The semicolon (;) should not be included at the end of the macro definition because a macro definition ends with a newline, not a semicolon.

2. The value of 82 is assigned to result due to the assignment expression result =

1 + 9 * 9.

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500

Appendix B

3. The message of Under #else. is printed out.

4. The message of Under #ifdef. is printed out.

Exercises

1. The following is one possible solution:

/* 23A01.c */

#include

/* main() function */

main()

{

#define human 100

#define animal 50

#define computer 51

#define SUN 0

#define MON 1

#define TUE 2

#define WED 3

#define THU 4

#define FRI 5

#define SAT 6

printf(“human: %d, animal: %d, computer: %d\n”,

human, animal, computer);

printf(“SUN: %d\n”, SUN);

printf(“MON: %d\n”, MON);

printf(“TUE: %d\n”, TUE);

printf(“WED: %d\n”, WED);

printf(“THU: %d\n”, THU);

printf(“FRI: %d\n”, FRI);

printf(“SAT: %d\n”, SAT);

return 0;

}

2. The following is one possible solution:

/* 23A02.c */

#include

#define MULTIPLY(val1, val2) ((val1) * (val2))

#define NO_ERROR 0

main(void)

{

int result;

result = MULTIPLY(2, 3);

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501

printf(“MULTIPLY(2, 3) produces value of %d.\n”, result);

return NO_ERROR;

}

3. The following is one possible solution:

/* 23A03.c */

#include

#define UPPER_CASE 0

#define NO_ERROR 0

main(void)

{

#if UPPER_CASE

printf(“THIS LINE IS PRINTED OUT,\n”);

printf(“BECAUSE UPPER_CASE IS DEFINED.\n”);

#elif LOWER_CASE

printf(“This line is printed out,\n”);

printf(“because LOWER_CASE is defined.\n”);

#else

printf(“This line is printed out,\n”);

printf(“because neither UPPER_CASE nor LOWER_CASE is defined.\n”);

#endif

B

return NO_ERROR;

}

4. The following is one possible solution:

/* 23A04.c: */

#include

#define C_LANG ‘C’

#define B_LANG ‘B’

#define NO_ERROR 0

main(void)

{

#if C_LANG == ‘C’

#if B_LANG == ‘B’

#undef C_LANG

#define C_LANG “I know C language.\n”

#undef B_LANG

#define B_LANG “Also, I know BASIC.\n”

printf(“%s%s”, C_LANG, B_LANG);

#else

#undef C_LANG

#define C_LANG “I only know C language.\n”

printf(“%s”, C_LANG);

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Appendix B

#endif

#elif B_LANG == ‘B’

#undef B_LANG

#define B_LANG “I only know BASIC.\n”

printf(“%s”, B_LANG);

#else

printf(“I don’t know C or BASIC.\n”);

#endif

return NO_ERROR;

}

34 067231861x index 1/25/00 10:45 AM Page 503

INDEX

~ (bitwise complement

== (equal to operator),

Symbols

operator), 131

98

| (bitwise OR operator),

\ (escape character), 59

+= (addition assignment

131

%% format specifier, 79

operator), 93

^ (bitwise XOR opera-

> (greater than opera-

& (ampersand)

tor), 131

tor), 98

address-of operator,

{} (braces), 45, 48

>= (greater than or equal

177-179

if statement, 156

to operator), 98

bitwise AND operator,

if-else statement, 159

++ (increment operator),

131

[ ] (brackets), 190

96-98

<> (angle brackets), 32

*/ (closing comment

<< (left-shift operator),

-> (arrow operator),

mark), 29

133-135

unions, 335, 351

:? (conditional operator),

< (less than operator), 98

= (assignment operator),

135-136

<= (less than or equal to

92

-- (decrement operator),

operator), 98

* (asterisk)

96-98

&& (logical AND opera-

deference operator, 182

/= (division assignment

tor), 124-126

determining meaning,

operator), 93

! (logical NEGATION

182

. (dot operator), unions,

operator), 128-129

multiplication operator,

335-337, 351

|| (logical OR operator),

182

” (double quotes), 32-33,

126-127

pointers, 180

59

*= (multiplication assign-

ment operator), 93

34 067231861x index 1/25/00 10:45 AM Page 504

504

!= (not equal to operator)

!= (not equal to opera-

ftell() function,

built-in

tor), 98

374-378

main() functions,

\0 (null character), 198

sequential disk files,

306

/* (opening comment

374

naming, 308

mark), 29

accessing

replacing, 308

// (opening comment

array elements, indexes,

command-line, 305

mark), 30

190

receiving, 306-308

() (parentheses)

arrays, via pointers,

passing to functions,

if statement, 156

264-266

47-48, 305

placing around expres-

addition assignment

variable, processing,

sions, 419

operator (+=), 93

252-254

% (remainder operator),

address variables.
See

argv arguments, 306

43

pointers

arithmetic assignment

%= (remainder assign-

address-of operator (&),

operators, 92-95

ment operator), 93

177-179, 323

addition assignment

>> (right-shift operator),

addresses

(+=), 93

133-135

left value, 176

division assignment

; (semicolons), 28

memory, 343

(/=), 93

’ (single quotes), 59

algorithms, implement-

multiplication assign-

-= (subtraction assign-

ing, 305

ment (*=), 93

ment operator), 93

aligning output, 83-84

remainder assignment

- (subtraction operator),

allocating memory

(%=), 93

96

calloc() function,

subtraction assignment

- (unary minus operator),

286-288

(-=), 93

95

malloc() function,

arithmetic expressions,

19L02.exe executable,

280-283

#if directive, 406

318

American National

arithmetic operators,

Standards Institute.
See

43-44

ANSI

array data type, 424

angle brackets (<>), 32

array element references,

A

ANSI (American

191

National Standards

array subscript operator

access

Institute), 15

([ ]), 190

random

C standard, 15-16

arrays, 190

code example,

header files, 439

accessing via pointers,

375-378

applying static specifiers,

264-266

disk files, 374-377,

230-231

character, 190, 210-211

387

argc arguments, 306

displaying, 196-198

fseek() function,

argument lists, 47

initializing, 208-209

374-378

arguments

declaring, 190

argc, 306

argv, 306

34 067231861x index 1/25/00 10:45 AM Page 505

books

505

elements, 190

integers to structures,

binary operators, multi-

accessing, 190

315

plication (*), 182

initializing, 191-192

inter values to enum

binary streams, 356, 370

integers, 190

data types, 296, 300