1. Loops

2. Variable initialization
All uninitialized values are random / garbage values!
C doesn’t zero-initialize anything unless explicitly told
Never use a value from an uninitialized variable
Extremely important for counters, sums, products etc.
You can initialize variables when declaring.
Don’t initialize more than 1 value per line! (coding style)
int value = 0;
float value = 4.32;
char value = "Hello, world!";
2018
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3. Loops Allows repeated execution of a block of code
Loop condition determines for how long the loop runs
Loop may never run – condition is false when execution reaches the loop
Loop can run infinitely – the condition never becomes false
Control statements
Break – breaks out of the loop, condition is ignored
Continue – forces the next iteration of a loop, skipping any code still to run
Loop iterator – a counter to limit for how many times the loop runs
It’s possible to nest loops for more complex tasks.
2018
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4. Loop condition Condition is checked before the loop body is executed:
While loop
For loop
Condition is checked after the loop body has executed:
do while loop
It’s possible for while and for loops to never run. This happens if the condition is false when code execution reaches the loop
Do while loop will always run at least once!
2018
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5. while loop (checked before execution)
while (condition) {
loop body }
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6. do while loop (checked after execution){
loop body }
while (condition);
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7. for loop (checked before execution)
for (initialization; condition; afterthought) {
loop body }
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8. Math
The right side of the equal sign (rvalue) is evaluated (calculated) and stored to the variable on the left (lvalue) c = a + b; c = c + b; c += b;
Incrementing and decrementing variables a = a + 1; a += 1; a++; a--;
NB! Don’t forget to initialize products, sums etc!
2018
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9. Examples of using loops
while
do while
for
i = 0; while (i < 10) { printf("%d\n", i); i++; }
i = 0; do { printf("%d\n", i); i++; } while (i < 10);
for (i = 0; i < 10; i++) { printf("%d\n", i); }
2018
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10. Things to consider When will my loop run? Will my loop run at all?
When will my loop stop?
Will my loop stop at all?
Does my loop run exactly the correct amount of times?
off-by-one errors
2018
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11. Home task
Create a simple calendar application, that asks the user for the day of the week and time
The day of the week is outputted based on the number input from user (e.g. 2 – Tuesday)
The location/appointment/task is outputted based on the time specified (e.g. T 8:00 – Programming I lecture at U05-103)
Advanced: write the program in a loop, so that the day and time can be queried again without exiting (rerunning) the program.
Create an algorithm based on the code You made in the lab (sum)
Use a modelling tool this time
Make 3 versions total - with each of the loops
Use swim lanes to divide your program into segments
2018
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12. Lab task
Create a program that asks for the user for 5 numbers and adds them up
The current sum is displayed after every addition
Create the same program using three different types of loops!
2018
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13. Lab task (advanced, more points)
Using nested loops, create a filled triangle, base length 10 pcs
In the end of every row, show the number of blocks in this row and total used
Still boring?
Mirror the triangle to start from the right
…or do it both ways in a single run
Ask the user for base length
2018
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