Session 2 Summary

This is all here: http://www.bath.ac.uk/%7Epy8ieh/academic/ccourse/

***** Q2.1:

#include <stdio.h> /* for input/output */

main() {
  int integerVariable1, integerVariable2;
  printf("Lab Session 2, Question 2.1\n"); /* Display program header */
  integerVariable1 = 1; /* Assign first number */
  integerVariable2 = 2; /* Assign second number */
  printf("result: %i+%i=%i\n", 
         integerVariable1, 
         integerVariable2, 
         integerVariable1+integerVariable2); /* Add numbers together and print the result */
}

/* OUTPUT:
Lab Session 2, Question 2.1
result: 1+2=3
 */



***** Q2.2:

#include <stdio.h> /* for input/output */

main() {
  float floatVariable1, floatVariable2;
  printf("Lab Session 2, Question 2.2\n"); /* Display program header */
  floatVariable1 = 0.1; /* Assign first number */
  floatVariable2 = 0.2; /* Assign second number */
  printf("result: %f+%f=%f\n", 
         floatVariable1, 
         floatVariable2, 
         floatVariable1+floatVariable2); /* Add numbers together and print the result */
}

/* OUTPUT:
Lab Session 2, Question 2.2
result: 0.100000+0.200000=0.300000
 */



***** Q2.3:

#include <stdio.h> /* for input/output */

main() {
  float floatVariable1, floatVariable2;
  printf("Lab Session 2, Question 2.3\n"); /* Display program header */
  printf("Enter two floating point numbers separated by a space: ");
  scanf("%f %f", &floatVariable1, &floatVariable2); /* Get the numbers from the user */
  printf("result: %f+%f=%f\n", 
         floatVariable1, 
         floatVariable2, 
         floatVariable1+floatVariable2); /* Add numbers together and print the result */
}

/* OUTPUT:
Lab Session 2, Question 2.3
Enter two floating point numbers separated by a space: 3.2e-1 1e-2
result: 0.320000+0.010000=0.330000
 */



***** Q2.4:

#include <stdio.h> /* for input/output */

main() {
  char TheLovelyCharacterThatTheUserGaveUs;
  printf("Lab Session 2, Question 2.4\n"); /* Display program header */
  printf("Enter a lovely character: "); /* Prompt the user */
  scanf("%c", &TheLovelyCharacterThatTheUserGaveUs); /* Get the character from the user */
  printf("You typed: '%c'\n", TheLovelyCharacterThatTheUserGaveUs); /* Print it out again */
}

/* OUTPUT:
Lab Session 2, Question 2.4
Enter a lovely character: g
You typed: 'g'
 */


***** Q2.5:

#include <stdio.h> /* for input/output */

/* WARNING: This program does not accept multibyte characters!!! */

main() {
  char TheLovelyCharacterThatTheUserGaveUs;
  printf("Lab Session 2, Question 2.5\n"); /* Display program header */
  printf("Enter a lovely character: "); /* Prompt the user */
  scanf("%c", &TheLovelyCharacterThatTheUserGaveUs); /* Get the character from the user */
  printf("I think that that character has the integer value %i.\n", TheLovelyCharacterThatTheUserGaveUs); 
     /* Print it out again, effectively casting the character as an integer (hmm!). */
}

/* OUTPUT:
Lab Session 2, Question 2.5
Enter a lovely character: 6
I think that that character has the integer value 54.
 */

/* SEQUENCE:
space, numbers, capital letters, lowercase letters, symbols interspersed everywhere.
  ' ' = 32
  '0' = 48
  '1' = 49
  '9' = 57
  'A' = 65
  'Z' = 90
  'a' = 97
  'z' = 122
 */



***** Q3.1:

main() {
  float x;
  x = sin(30);
  printf("%f\n",x);
}

/* COMPILER OUTPUT:
Compiling was fine, but sin(30) gave answer 30.000!!! :-/
 */

/* REASON: 
Did not refer to the math library so sin() is unknown.
 */


***** Q3.2:

#include <stdio.h> /* for input/output */
#include <math.h> /* for sin */ 

main() {
  float x;
  x = sin(30);
  printf("%f\n",x);
}

/* OUTPUT:
-0.988032
 */

/* NOTES:
Added
   #include <math.h>
...to correct problem. 
 */

/* NOTES:
Unlike the expectations of others, sin(30) will of course give 
sin(30 radians) not sin(30 degrees).
 */


***** Q3.3:

#include <stdio.h> /* for input/output */
#include <math.h> /* for asin */ 

main() {
  float x;
  x = asin(1.0);
  printf("%f\n",x);
}

/* OUTPUT:
1.570796
 */

/* (which is pi/2) */


***** Q3.4:

#include <stdio.h> /* for input/output */
#include <math.h> /* for cbrt, sqrt, hypot */ 

main() {
  float cbrtResult, sqrtResult, hypotResult;
  cbrtResult = cbrt(27); /* cube root of 27 */
  sqrtResult =  sqrt(9); /* square root of 9 */
  hypotResult = hypot(3,4); /* the hypotenuse of the 3,4,5 triangle */
  printf("cbrt(27) = %f\nsqrt(9) = %f\nhypot(3,4) = %f\n", 
         cbrtResult, sqrtResult, hypotResult); /* print results */
}

/* OUTPUT:
cbrt(27) = 3.000000
sqrt(9) = 3.000000
hypot(3,4) = 5.000000
 */

/*
cbrt - cube root
sqrt - square root
hypot - find the hypotenuse of a right angled triangle
 */


***** Q4.1:

#include <stdio.h> /* for input/output */

main() {
  int x=10;
  printf("Lab Session 2, Question 4.1\n"); /* Display program header */
  while(--x) {
    printf("%f\n",(float)5/x);
  }
}

/* OUTPUT:
0.555556
0.625000
0.714286
0.833333
1.000000
1.250000
1.666667
2.500000
5.000000
 */

/* ANSWER:
what it does: start at 9 and count down to 1, displaying five divided
by the number for each step of the way.

float statement: to cast the 5/x as a float result, otherwise it would
be trying to do it as an integer calculation which would be a lot less
accurate (and which the %f specifier would not interpret correctly).

stop: the loop stops executing when x reaches 0, since it is reduced
by one before each loop.
 
 */


***** Q5.2:

#include <stdio.h> /* for input/output */
#include <math.h> /* for pow */

main() {
  double y;
  int bits = 0; /* set bits to 0 */
  int base = 2; /* assume computer uses binary */
  do {
    bits++; /* increase number of bits known to exist */
    y = pow(base, bits+1); /* test next number of bits */ 
  } while (y != y+1); /* stop if 1 is no longer significant */
  printf ("C uses %d bits for the mantissa of a double.\n", bits);
}


***** Q5.4:

/* COMPILATION ERRORS 
"s3q5-2.c", line 10: syntax error before or at: y
cc: acomp failed for s3q5-2.c
 -- solved by linking in the math library
 */


***** Q5.5:

/* OUTPUT:
C uses 52 bits for the mantissa of a double.
 */

/* This is what the documentation says! */

****** END;