11. Now, let try characters and strings. A string is nothing more than a collection of characters. The number of characters are in the brackets, [ ] minus one (reserved for terminating null, or null character or ‘\0’ to mark the end of the string) gives the length of the string. The following t, an array variable can store a string that is 10 characters long.

// needed for printf()

#include<stdio.h>

int main()

{

     char a ='W';

     char t[11] = "PeAcE";

      printf(" a = %c\n", a);

     printf(" t = %s\n", t);

     return 0;

}

1. Name the character variable.

2. Name the string variable.

3. Is a character enclosed between single quotes or double quotes?

4. Is a string enclosed between single quotes or double quotes?

1. a.

2. t.

3. single quotes.

4. double quotes.

12. Since strings are collection of characters, not single items, they need to be treated differently from other basic data type such as integers, floats and characters. Let trystrcpy_s() function (this is a secure version of strcpy()), which defined in the string.h header file.

// needed for printf()

#include<stdio.h>

// needed for strcpy() family

#include<string.h>

int main()

{

     char a ='W', b;

     char t[20] = "The copied PeAcE", q[20];

      b = a;

      strcpy_s(q, 20, t);

     printf("b = %c\n", b);

      printf("t = %s\n", t);

     return 0;

}

1. How is a character assigned to a character variable?

2. How is a string assigned to a string variable?

1. A character must be in single quotes.

2. A string must be in double quotes.

13. Let swap the values of t and r.

// needed for printf()

#include<stdio.h>

// needed for strcpy() family

#include<string.h>

int main()

{

     char t[20] = "The copied PeAcE", q[20], r[20];

      strcpy_s(r, 20, "Copied to r");

      strcpy_s(q, 20, t);      // t to q

      strcpy_s(r, 20, q);     // q to r

      strcpy_s(t, 20, r);      // r to t

     printf("t = %s\n", t);

     printf("q = %s\n", q);

      printf("r = %s\n", r);

     return 0;

}

1. What value was assigned to r?

2. What value was assigned to q?

3. What value was assigned to t?

4. Now what value was assigned to r?

1. "Copied to r" string.

2. "The copied PeAcE" string.

3. "The copied PeAcE" string.

4. "The copied PeAcE" string.

In this program, the t array contains "The copied PeAcE" string. Then "Copied to r" string been copied to array r. Next, arrayt been copied to arrayq, so q contains "The copied PeAcE". Next, array q been copied to r so we have "The copied PeAcE" string in r. Finallyr been copied to t so we have "The copied PeAcE" string inr. At the end all the array will contain "The copied PeAcE" string.

14. Show the output for the following code. Study the source code and the output.

(a)       // needed for printf()

#include<stdio.h>

void main(void)

{

     int i = 3, j = 5;

      i = i + 1;

      j = j + i + 1;

      printf("%d %d\n", i + 1, j - 1);

      printf("%d %d\n", i, j);

}

For the first printf() the current value of i is 4 andj is 10 as shown in the secondprintf().

(b)       // needed for printf()

#include<stdio.h>

void main(void)

{

     double x = 13.5, y = -23.2;

      x = (x / 2) * -1 + y;

      y = 13 / 2 - 2;

      printf("%f %.2f\n", x, y);

}

Considering the operator precedence, i n the first expression we have:

x = (13.5/2)*-1+(-23.2)

x=6.75*-1+(-23.2)

x=-6.75-23.2

x=-29.950000 (default to 6 floating point precision)

In the second expression:

y=13/2 -2

y=6-2 (truncated to an integer because both numerator and denominator are integers)

y=4.00 (to 2 floating point precision)

(c)       // needed for printf()

#include<stdio.h>

// needed for strcpy_s()

#include<string.h>

void main(void)

{

     // Note that we just initialize b to a space, s to a comma just for dummy...

     char a ='b', b = ' ', s[21] = ",", t[21] = "OvEr", r[21] = "RoLl";

      printf("a = %c b = %c r = %s s = %s t = %s\n", a, b, r, s, t);

      b = a;

      a = 'c';

      strcpy_s(s, 21, r);

      strcpy_s(r, 21, t);

      strcpy_s(t, 21, s);

      printf("a = %c b = %c r = %s s = %s t = %s\n", a, b, r, s, t);

}

Before the first strcpy_s(), the current value for the variables are:

a='c', b='b', s=,, t="OvEr" and r="RoLl"

The first strcpy_s() copies "RoLl" string tos so s contains "RoLl" string. The secondstrcpy_s() copies "OvEr" string to r so r contains "OvEr" string and the thirdstrcpy_s() copies "RoLl" string to t so t contains "RoLl" string.

15. Declare me as an integer. Assign it the value of 40. Declare you as an integer and assign it the value of 20. Declare average as a float and assign it the average of me and you. Then using one printf() for each line, print the following. The numbers are printed using the values of the variables. The last line starts on a tab position.

-----------Output-----------

I am 40.

You are 20

      We are around 30!

#include <stdio.h>

void main(void)

{

       int me = 40, you = 20;

       float average = 0.0;

      // the (float) is a simple C type promotion. Here we promote

       // the integer type to float before assign it to

       // average variable

      average = (float)((me+you)/2);

      printf("I am %d\n", me);

      printf("You are %d\n", you);

      printf("\tWe are around %.0f\n", average);

}

16. Declare a string called name that can hold up to 20 characters including the terminating null character. Declarerate as afloat and hours as an integer. Now assign “Garfield”,10.0 and 20 to these variables respectively. Without creating any new variables, print the following using the values of name,rate and hours. Use one printf() for each line that is printed.

---------Output-----------

His name is Garfield,

Rate is 10.00 and the hours worked was 20

Garfield made 200.00 dollars.

#include <stdio.h>

void main(void)

{

    char name[20]= "Garfield";

    float rate = 0.0;

    int hours = 0;

    rate = 10.0;

    hours = 20;

    printf("His name is %s\n", name);

    printf("Rate is %.2f and the hours worked was %d\n", rate, hours);

    printf("Garfield made %.2f dollars.\n", rate*hours);

}

17. Study the first program example in this Module. Find the codes that you don’t understand and discuss with your partner/group member to find the answers. Then create four questions and answers.

18. From time to time we will use the functions from the standard library that normally come together with your compiler. For example, we can use the mathematical functions such as square root (sqrt()) and power-to (pow()) functions from math.h header. Run the following program and show the output.

// needed for printf()

#include<stdio.h>

// needed for math functions such as sqrt()

#include<math.h>

void main(void)

{

     // study this funny part, add 1 before and add 1 after...

     int i = 1, j;

      ++i; // i = i + 1

      printf("i = %d\n", i);

      j = ++i; // j = i = i + 1 - i already equal to 2

      printf("j = %d\n", j);

      j = i++; // assign i to j and then i = i + 1

      printf("i = %d j = %d\n", i, j);

     // using functions from standard library, math.h

      printf("Square root of 9 is %f\n", sqrt(9));

      printf("2 raised to the power of 3 is %f\n", pow(2, 3));

}

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

19. By considering the operator precedence, convert the following equation to C expression.

    ((3 + (4*x)) / 5) - (10*((y-5)*(a+b+c)))/x + (9*((4/x) + ((9+x)/y)))

    sqrt(pow(x,2) + pow(y,2))

    (-b + sqrt((b * b) - (4 * a * c))) / (2 * a)

20. Convert the following C expression to mathematical expression.

21. Based on the C operator precedence and associativity, state the execution order of the following expressions.

22. Convert the following mathematical expressions to C expressions.

1. (rate*rate) + delta

2. 2*(salary + bonus)

3. 1/(time + (3*mass))

4. (a - 7) / (t + (9 * v))

Using Compiler’s Documentation

The best resource of programming is the documentation that comes together with your compiler. Using the compiler’s documentation means we refer to the authoritative source of reference. In practice #18 you have been introduced with sqrt() and pow() functions that defined in math.h header file. From the previous lab practice you should already know how to find the math.h header file in your machine.

What about the information for sqrt() and pow() functions? How to use those functions? How to write a proper syntax? Now you will learn how to dig that information.

1. While in your Visual C++ 2005 EE, selectHelp →Index menu (make sure you have installed the MSDN library).

2. Type “run-time libraries” in the Look for: field and then click the highlighted “run-time libraries” just under the Look for: field. The information page for the run-time libraries is displayed on the right window.

3. You can see that for C programming, Visual C++ 2005 (Microsoft) called C Run-Time (CRT) Libraries. The Microsoft CRT contains much more than the Standard C Library. There is a lot of information that you need to filter out to find your specific information. For this practice we just want to find information for square root function (sqrt()).

4. Click the Alphabetical Function Reference link.

5. Next, scroll down the page until you find sqrt,sqrtf and click the link.

6. You will find a complete sqrt() information that includes: the prototype, parameter, return value, required header file, program example and .Net framework equivalent class.