ch1-Temperature Programs

Chapter_1      ch1-Hello                                                                                ch1-Chars 

Contents:

temp.c     Right-justified      tempf.c     truncate.c      Exercise_1-3      Exercise_1-4     for()_variant     Exercise_1-5      #define 

temp.c     K&R, p. 9     (Fahrenheit-Celsius)     download 

#include <stdio.h> // for printf()

/*

print Fahrenheit-Celsius table

for fahr = 0, 20, ..., 300

*/

int main()

{

  int fahr, celsius; // main vars used for output

  int lower, upper, step; // vars used for computation

  lower = 0; // lower limit of temperature table

  upper = 300; // upper limit

  step = 20; // step size

  fahr = lower;

  while(fahr <= upper)

  {

    celsius = 5 * (fahr-32) / 9;

    printf("%d\t%d\n", fahr, celsius);

    fahr += step; // fahr = fahr + step;

  }

}

/*

gcc temp.c -o temp

./temp

0       -17

20      -6

40      4

60      15

80      26

100     37

120     48

140     60

160     71

180     82

200     93

220     104

240     115

260     126

280     137

300     148

*/

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Right-justified     K&R, p. 11     (temperature, Fahrenheit-Celsius)

tempr.c          download 

#include <stdio.h> // for printf()

/*

print Fahrenheit-Celsius table

for fahr = 0, 20, ..., 300

*/

int main()

{

  int fahr, celsius; // main vars used for output

  int lower, upper, step; // vars used for computation

  lower = 0; // lower limit of temperature table

  upper = 300; // upper limit

  step = 20; // step size

  fahr = lower;

  while(fahr <= upper)

  {

    celsius = 5 * (fahr-32) / 9;

    printf("%3d\t%3d\n", fahr, celsius);

    fahr += step; // fahr = fahr + step;

  }

}

/*

gcc tempr.c -o tempr

./tempr

  0     -17

 20      -6

 40       4

 60      15

 80      26

100      37

120      48

140      60

160      71

180      82

200      93

220     104

240     115

260     126

280     137

300     148

*/

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tempf.c     K&R, p. 12     (floating-point version)     download 

#include <stdio.h> // for printf()

/*

print Fahrenheit-Celsius table

for fahr = 0, 20, ..., 300

(floating-point version)

*/

int main()

{

  float fahr, celsius; // main vars used for output

  int lower, upper, step; // vars used for computation

  lower = 0; // lower limit of temperature table

  upper = 300; // upper limit

  step = 20; // step size

  fahr = lower;

  while(fahr <= upper)

  {

    celsius = (5.0 / 9.0) * (fahr-32.0);

    printf("%3.0f %6.1f\n", fahr, celsius);

    fahr += step; // fahr = fahr + step;

  }

}

/*

gcc tempf.c -o tempf

./tempf

  0  -17.8

 20   -6.7

 40    4.4

 60   15.6

 80   26.7

100   37.8

120   48.9

140   60.0

160   71.1

180   82.2

200   93.3

220  104.4

240  115.6

260  126.7

280  137.8

300  148.9

*/

Note:  In the previous programs (temp.c, Right-justified), the Celsius values have been truncated to the lower integer value (see also truncate.c).

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truncate.c     (float to int)     download 

#include <stdio.h> // for printf()

int main()

{

  printf("5 / 2 = %d\n", 5 / 2); // truncate, print as int

  printf("5.0 / 2 = %g\n", 5.0 / 2);

  printf("5 / 2.0 = %g\n", 5 / 2.0);

  printf("(float) (5 / 2) = %g\n", (float) (5 / 2)); // truncate: (float) 2

  printf("(float) 5 / 2 = %g\n", (float) 5 / 2); // ((float) 5) / 2

  printf("5 / (float) 2 = %g\n", 5 / (float) 2); // 5 / ((float) 2)

  float x = 5, y = 2; // convert int to float in assignments

  printf("x / y = %g\n", x / y);

}

/*

gcc truncate.c -o truncate

./truncate

5 / 2 = 2

5.0 / 2 = 2.5

5 / 2.0 = 2.5

(float) (5 / 2) = 2

(float) 5 / 2 = 2.5

5 / (float) 2 = 2.5

x / y = 2.5

*/

Note:  See also C_type_conversion on W3Schools, the C_Tutorial, chapter C_Data_Types.

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Exercise 1-3     K&R, p. 13     (Temperature heading)

Exercise 1-3. Modify the temperature conversion program to print a heading above the table.

tempfh.c          download 

#include <stdio.h> // for printf()

/*

print Fahrenheit-Celsius table

for fahr = 0, 20, ..., 300

(floating-point version with heading)

*/

int main()

{

  float fahr, celsius; // main vars used for output

  int lower, upper, step; // vars used for computation

  lower = 0; // lower limit of temperature table

  upper = 300; // upper limit

  step = 20; // step size

  // Heading:

  printf("Fahrenheit-Celsius\n");

  printf("conversion table\n");

  printf("------------------\n");

  fahr = lower;

  while(fahr <= upper)

  {

    celsius = (5.0 / 9.0) * (fahr-32.0);

    printf("%3.0f %6.1f\n", fahr, celsius);

    fahr += step; // fahr = fahr + step;

  }

}

/*

gcc tempfh.c -o tempfh

./tempfh

Fahrenheit-Celsius

conversion table

------------------

  0  -17.8

 20   -6.7

 40    4.4

 60   15.6

 80   26.7

100   37.8

120   48.9

140   60.0

160   71.1

180   82.2

200   93.3

220  104.4

240  115.6

260  126.7

280  137.8

300  148.9

*/

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Exercise 1-4     K&R, p. 13     (Celsius to Fahrenheit, temperature)

Exercise 1-4. Write a program to print the corresponding Celsius to Fahrenheit table.

Contents:     celsius1.c     celsius2.c 

celsius1.c          download 

#include <stdio.h> // for printf()

/*

print Celsius-Fahrenheit table

for celsius = 0, 20, ..., 300

(floating-point version)

*/

int main()

{

  float celsius, fahr; // main vars used for output

  int lower, upper, step; // vars used for computation

  lower = 0; // lower limit of temperature table

  upper = 300; // upper limit

  step = 20; // step size

  printf("Celsius-Fahrenheit\n");

  printf("conversion table\n");

  printf("------------------------\n");

  celsius = lower;

  while(celsius <= upper)

  {

    fahr = (9.0 / 5.0) * celsius + 32.0;

    printf("%3.0f %6.1f\n", celsius, fahr);

    celsius += step; // celsius = celsius + step;

  }

}

/*

gcc celsius1.c -o celsius1

./celsius1

Celsius-Fahrenheit

conversion table

------------------------

  0   32.0

 20   68.0

 40  104.0

 60  140.0

 80  176.0

100  212.0

120  248.0

140  284.0

160  320.0

180  356.0

200  392.0

220  428.0

240  464.0

260  500.0

280  536.0

300  572.0

*/

Note: (9.0 / 5.0)  multiplied with a multiple of 10 gives an integer, but we should keep celsius and fahr as float variables for computations.  In order to get similar results as before, we can choose the interval  -20...150  and the  step 10.

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celsius2.c          download 

#include <stdio.h> // for printf()

/*

print Celsius-Fahrenheit table

for celsius = -20, -10, 0, 10, ..., 150

(floating-point version)

*/

int main()

{

  float celsius, fahr; // main vars used for output

  int lower, upper, step; // vars used for computation

  lower = -20; // lower limit of temperature table

  upper = 150; // upper limit

  step = 10; // step size

  printf("Celsius-Fahrenheit\n");

  printf("conversion table\n");

  printf("------------------------\n");

  celsius = lower;

  while(celsius <= upper)

  {

    fahr = (9.0 / 5.0) * celsius + 32.0;

    printf("%3.0f %6.0f\n", celsius, fahr);

    celsius += step; // celsius = celsius + step;

  }

}

/*

gcc celsius2.c -o celsius2

./celsius2

Celsius-Fahrenheit

conversion table

------------------------

-20     -4

-10     14

  0     32

 10     50

 20     68

 30     86

 40    104

 50    122

 60    140

 70    158

 80    176

 90    194

100    212

110    230

120    248

130    266

140    284

150    302

*/

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for() variant     (temperature)

Note:  while() should be used when testing a condition, for() should be used when counting something.

fahr.c     K&R, p. 13          download 

#include <stdio.h> // for printf()

// print Fahrenheit-Celsius table

int main()

{

  int fahr;

  for (fahr = 0; fahr <= 300; fahr += 20)

    printf("%3d %6.1f\n", fahr, (5.0/9.0)*(fahr-32));

}

/*

gcc fahr.c -o fahr

./fahr

  0  -17.8

 20   -6.7

 40    4.4

 60   15.6

 80   26.7

100   37.8

120   48.9

140   60.0

160   71.1

180   82.2

200   93.3

220  104.4

240  115.6

260  126.7

280  137.8

300  148.9

*/

TIP:  It is always good coding practice to put braces around the body of a loop, like  while() or for(), even if the body contains a single statement. It is easier to read, to distinguish from other code, and you may add more statements to the body later on. In our program,

for (fahr = 0; fahr <= 300; fahr += 20)

{printf("%3d %6.1f\n", fahr, (5.0/9.0)*(fahr-32));}

Note:  Write

while(){i++;},  not

while(){i++}; // compile error

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Exercise 1-5    K&R, p. 14     (Temperature reverse)

Exercise 1-5. Modify the temperature conversion program to print the table in reverse order, that is, from 300 degrees to 0.

fahrr.c          download 

#include <stdio.h> // for printf()

// print Fahrenheit-Celsius table in reverse order

int main()

{

  int fahr;

  for (fahr = 300; fahr >= 0; fahr -= 20)

  {printf("%3d %6.1f\n", fahr, (5.0/9.0)*(fahr-32));}

}

/*

gcc fahrr.c -o fahrr

./fahrr

300  148.9

280  137.8

260  126.7

240  115.6

220  104.4

200   93.3

180   82.2

160   71.1

140   60.0

120   48.9

100   37.8

 80   26.7

 60   15.6

 40    4.4

 20   -6.7

  0  -17.8

*/

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#define directive    K&R, p. 15     (temperature)

define.c          download 

#include <stdio.h> // for printf()

#define  LOWER 0   // lower limit of table

#define  UPPER 300 // upper limit

#define  STEP  20  // step size

// print Fahrenheit-Celsius table

int main()

{

  int fahr;

  for (fahr = LOWER; fahr <= UPPER; fahr += STEP)

  {printf("%3d %6.1f\n", fahr, (5.0/9.0)*(fahr-32));}

}

/*

gcc -E define.c // preprocessing

// symbolic constants are replaced by their values:

# 8 "define.c" // what is actually compiled:

int main()

{

  int fahr;

  for (fahr = 0; fahr <= 300; fahr += 20)

  {printf("%3d %6.1f\n", fahr, (5.0/9.0)*(fahr-32));}

}

gcc define.c -o define // compile

./define // run the program

  0   17.8

 20   -6.7

 40    4.4

 60   15.6

 80   26.7

100   37.8

120   48.9

140   60.0

160   71.1

180   82.2

200   93.3

220  104.4

240  115.6

260  126.7

280  137.8

300  148.9

*/

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