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**“C Programming Language (2nd Edition)“**popularly known as K & R C book.In this blog post I will give links to all the exercises from Chapter 4 of the book for easy reference.

**Chapter 4: Functions and Program Structure**

**Exercise 4-1.**Write the function strrindex(s,t) , which returns the position of the rightmost occurrence of t in s , or -1 if there is none.

Solution to Exercise 4-1.**Exercise 4-2.**Extend atof to handle scientific notation of the form 123.45e-6 where a floating-point number may be followed by e or E and an optionally signed exponent.

Solution to Exercise 4-2.**Exercise 4-3.**Given the basic framework, it’s straightforward to extend the calculator. Add the modulus ( % ) operator and provisions for negative numbers.

Solution to Exercise 4-3.**Exercise 4-4.**Add commands to print the top element of the stack without popping, to duplicate it, and to swap the top two elements. Add a command to clear the stack.

Solution to Exercise 4-4.**Exercise 4-5.**Add access to library functions like sin , exp , and pow . Seein Appendix B, Section 4.

Solution to Exercise 4-5.**Exercise 4-6.**Add commands for handling variables. (It’s easy to provide twenty-six variables with single-letter names.) Add a variable for the most recently printed value.

Solution to Exercise 4-6.**Exercise 4-7.**Write a routine ungets(s) that will push back an entire string onto the input. Should ungets know about buf and bufp , or should it just use ungetch ?

Solution to Exercise 4-7.**Exercise 4-8.**Suppose that there will never be more than one character of pushback. Modify getch and ungetch accordingly.

Solution to Exercise 4-8.**Exercise 4-9.**Our getch and ungetch do not handle a pushed-back EOF correctly. Decide what their properties ought to be if an EOF is pushed back, then implement your design

Solution to Exercise 4-9.**Exercise 4-10.**An alternate organization uses getline to read an entire input line; this makes getch and ungetch unnecessary. Revise the calculator to use this approach.

Solution to Exercise 4-10.**Exercise 4-11.**Modify getop so that it doesn’t need to use ungetch. Hint: use an internal static variable.

Solution to Exercise 4-11.**Exercise 4-12.**Adapt the ideas of printd to write a recursive version of itoa ; that is, convert an integer into a string by calling a recursive routine.

Solution to Exercise 4-12.**Exercise 4-13.**Write a recursive version of the function reverse(s) , which reverses the string s in place.

Solution to Exercise 4-13.**Exercise 4-14.**Define a macro swap(t,x,y) that interchanges two arguments of type t . (Block structure will help.)

Solution to Exercise 4-14.

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