While Loops

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Del curso dictado por Duke University

Programming Fundamentals

296 calificaciones

Duke University

Programming Fundamentals

296 calificaciones

Curso 1 de 4 en SpecializationIntroduction to Programming in C

Programming is an increasingly important skill, whether you aspire to a career in software development, or in other fields. This course is the first in the specialization Introduction to Programming in C, but its lessons extend to any language you might want to learn. This is because programming is fundamentally about figuring out how to solve a class of problems and writing the algorithm, a clear set of steps to solve any problem in its class. This course will introduce you to a powerful problem-solving process—the Seven Steps—which you can use to solve any programming problem. In this course, you will learn how to develop an algorithm, then progress to reading code and understanding how programming concepts relate to algorithms.

De la lección

Reading Code

In this module, you will learn to read code—this means you will be able to execute a piece of code by hand, and clearly illustrate what each statement does and what the state of the program is. Understanding how to read code is the only way to be sure you can write correct code. By the end of this module, you will be able to read and understand code with functions, conditional statements, iteration, and other fundamental techniques.

While Loops3:23

Equivalent For and While Loops2:17

Execution of Nested Loops3:35

Execution of Continue2:56

Conoce a los instructores

Andrew D. Hilton
Associate Professor of the Practice
Electrical and Computer Engineering
Genevieve M. Lipp
Adjunct Professor
Electrical and Computer Engineering/Mechanical Engineering
Anne Bracy
Senior Lecturer
Computer Science, Cornell University

In this video,

we're going to demonstrate the execution of code containing a whie loop.

As always, we begin with the execution arrow at the start of main.

The first statement declares a variable x and

initializes it by calling g of 2 and 9.

Inside of g, we declare the variable total and

initialize it to 0, and then we reach a while loop.

The conditional expression of this while loop is

a less than b which in this case is 2 less than 9,

which is true, so we enter the body of the while loop.

The next statement is total plus equals a.

Remember that this is shorthand for total equals total plus a, so

total is going to equal 0 plus 2 which is 2.

We assign 2 to total and now we have a printf statement.

A = %d, b = %d new line,

where the first %d converts the value of a to a decimal number and

the second %d converts the value of b to a decimal number.

This prints out a = 2, b = 9.

The next statement is a ++.

Recall that this is shorthand for a = a + 1, so we're going to do a = 3.

B-- is shorthand for b = b- 1,

so we're going to do b = 8.

Now we've reached the close curly brace of the while loop, so

our execution arrow jumps right back up to the top of the while loop, right before

the conditional expression to determine if we should enter the body of the loop.

Evaluating the conditional expression gives 3 less than 8 which is true,

so we enter the body of the while loop again.

We do total +=a, 2+3 is 5,

so we update total.

Then, we're going to print a=3, b=8.

We're going to increment a by 1 and decrement b by 1.

We reach the close curly brace at the bottom of the while loop again, so

we jump back up to the top.

4 less than 7 is true, so we enter the body of the while loop.

Total += a, printf a=4, b=7, increment a and

decrement, jump back to the top of the loop.

5 less than 6 is true, so we enter the body of the while loop.

We execute each statement in the loop as before.

Now, however, when we get back to the top of the loop and

evaluate our conditional expression, we find 6 less that 5 is false.

Our execution arrow skips over the body of the loop and

begins executing statements immediately after it.

The value of total to return is 14, so we return that to main

leaving function g and returning our execution arrow back in to main

where we can now complete our initialization of x with x = 14.

We then continue executing statements in main.

We print out x = 14 and we return 0 exiting main and leaving the program.

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