Computer programming - Lab 1
Compiling your program
Compiling and running are two distinct steps.
The compiler converts the source file (.c) to an executable file.
Command: gcc options file.c
You should use these options (in any order)
- -Wall produce all types of warning messages. Your code should compile with no warnings (certainly without any warnings that you are absolutely sure don't matter).
- -O optimize. In the process, will warn about uninitialized variables. If your reason is to optimize, look up different variants.
- -std=c11 Use the latest standard (2011). Useful e.g. for local declarations in for. For older compilers, use -std=c99 .
- -lm Compile with the math library. Needed when you use functions from math.h
- -o execfile Use if you don't want the default name a.out for the generated executable.
To run your program, use the command
./a.out
where . (dot) means the current directory (where you compiled),
a.out is the executable file name (replace as needed) and /
is the directory separator character under Linux.
Simple functions with decisions
1. Write a function that takes three unsigned parameters and returns 1
if they can be the sides of a triangle and 0 otherwise.
2. A clerk works in an office, with a lunch break between 12:00 and 13:00.
A client comes with a task that takes two hours to solve. Write a function
that returns the time when the client can leave the office, given the time
when he arrives (an integer, i.e., on the hour).
3. Write a function that returns the median of three numbers (i.e., the
middle one, when ordering the numbers by value).
Integers, reals, rounding
4. Write a function that rounds its floating point argument to two
decimal places (i.e., to the closest real number with two decimal
places, away from zero). Example: 13.34295 is rounded to 13.34,
whereas -3.435 is rounded to -3.44. Choose from the following functions to
use: ceil, floor,
nearbyint, rint, round.
Recursion
5. Write a function that computes xn by repeated
squaring, i.e., if the exponent is even, we compute
e.g. x6 = (x2)3, which leaves
us with the simpler problem of computing the 3rd power (in the same way);
if the exponent is odd, we do likewise, and multiply again with the base:
x7 = (x2)3*x .
Write the function, first for unsigned, and then for integer exponent.
6. A really inefficient way of computing Fibonacci numbers is by using
the recurrence directly as given: F0 = 0,
F1 = 1, Fn = Fn-1 + Fn-2.
Figure out how many calls are needed to compute Fn.
Write a recursive function that computes this number efficiently.
7. A simple fractal figure can be produced from a square as follows:
if the side of the square is small (≤ 2), draw the square.
Else, split the square in 3x3 squares, do nothing for the four corner
squares, and draw recursively such a figure for the remaining five squares.
Marius Minea
Last modified: Sun Sep 29 0:30:00 EEST 2013