course content

Course Content

C Basics

1. Introduction

What is C?Structure of the C-ProgramStructure of the C-program 2/2How to Run the Program?

2. Data

DataVariablesPrintfArraysArrays 2/2Char and StringSizeofChallenge: PrintfChallenge: Sizeof

3. Operators

Assignment, Comparison, Not Equal ToSum, Difference, Increment, DecrementMultiplication, Division and ModuloComparison OperatorsChallenge: Comparison OperatorsLogical OperatorsChallenge: Logical Operators

4. Control Statements

If...Else OperatorChallenge: If...Else OperatorTernary OperatorSwitch, BreakWhile, Do...WhileFor, ContinueChallenge: For Loop

5. Functions

Structure of the FunctionDeclaration, Type and ReturnArgumentsChallenge: ArgumentsHeader, Prototypes Void, Recursion

6. Pointers

Pointers are around UsReferences and DereferencesPointersMalloc and FreeFunctions, Arrays and Two PointersVoid

C Basics

Functions, Arrays and Two PointersFunctions, Arrays and Two Pointers

Function with pointer

Let's try using a regular function to change the value of our data. For example, you need a function that would convert kilo-ohms to ohms (1 kOhm = 1000 Ohm).

c

Main.c

We were unable to change the value of the r variable. And all because not the value of the r variable itself is substituted into the function, but its copy.

In order for our program to make sense, we must substitute the address of the r variable into the function, therefore, the Ohm function must accept not double, but double*.

c

Main.c

Note that we are accessing the r variable twice. After using the Ohm function, the value of r has changed. And all because the function got not a copy but the original variable r address, and the function simply changed the value at the specified address.

Also, a function can return a pointer to an object that it itself has created:

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Main.c

Are arrays just pointers?

What do you think will happen if a number is added to the address?

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Main.c

If we add a number (pX + 1) to the address, we will get the address of the next memory cell!

Let's write a loop that will help us see the "sequence" of RAM:

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Main.c

We have looked ahead 3 steps. It turns out that among the received addresses, there is a clear hierarchy.

Since the int type takes up 4 bytes, we move forward 4 bytes per step. Very similar to an array!

It turns out that an array is just a constant address (which is hidden under the array's name) and allocated memory, and the index of the elements is their offset relative to the address of the first element!

We can prove this with the following program:

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Main.c

As you can see, we are not going straight through the array. We only use its address (the address of its first element).

Everything was clear?

Section 6. Chapter 5