C Programming Tutorial - 10 - Creating a Header File

Summary

This video tutorial introduces the concept of preprocessor directives in programming, focusing on 'include' and 'define'. The presenter explains how 'include' integrates external files like 'stdio.h' and 'stdlib.h' into the code, while 'define' creates constants with unchangeable values. The tutorial demonstrates creating a custom header file and using constants to calculate the age of girls one is allowed to date based on a humorous formula. The script concludes with a practical example, enhancing understanding of these fundamental programming concepts.

Takeaways

• 📝 The video discusses the concept of preprocessor directives in programming, which are lines at the top of a program that perform specific tasks before the program compiles.
• 🔍 The '#include' directive is used to include the contents of another file, such as 'stdio.h' or 'stdlib.h', into the program, facilitating the use of standard input/output functions like 'printf'.
• 🛠️ The process of converting code into a format that a computer can understand is called 'compiling'.
• 📚 The '#include' directive can be used with angle brackets for searching in default locations or double quotes for searching in the same directory as the source file.
• 🆕 The video introduces how to create a custom header file, which is a new file with a '.h' extension that can be included in the main program for reusability of code.
• 🔑 The '#define' directive is used to define constants, which are like variables but with values that cannot be changed once set.
• 🎨 Constants are typically written in all uppercase letters to distinguish them from variables in the code.
• 🔄 Preprocessor directives do not require a semicolon at the end, unlike regular C statements.
• 👨‍💻 The video demonstrates how to use a custom header file and constants in a program to calculate the age of girls the programmer is allowed to date, based on a simple formula.
• 😉 The presenter uses humor to engage the audience, suggesting they go find someone to date after learning the concept of constants and custom header files.
• 🔍 The video emphasizes the importance of understanding preprocessor directives as a fundamental part of programming in C.

Q & A

What are preprocessor directives used for in a program?

Preprocessor directives are used to give instructions to the preprocessor before the actual compilation of the program. They include files, define constants, and can perform other tasks before the code is translated into machine code.

What is the purpose of the '#include' directive?

The '#include' directive is used to include the contents of one file into another. It allows for the use of standard libraries like stdio.h and stdlib.h, and can also include custom header files created by the programmer.

What does the '<stdio.h>' header file provide?

'<stdio.h>' is a standard input/output header file that provides functions for input and output operations, such as printf for printing to the screen.

What is the difference between a variable and a constant in programming?

A variable is a named storage location that can hold a value which can be changed throughout the program. A constant, on the other hand, is a value that cannot be changed once it is set.

Why should constants be written in all uppercase letters?

Constants are written in all uppercase letters to distinguish them from variables. This is a convention that helps programmers quickly identify constants in the code.

What is the purpose of the '#define' directive?

'#define' is a preprocessor directive used to define constants. It replaces occurrences of the constant's name with its value throughout the program before compilation.

Why is it important to understand the process of compiling a program?

Understanding the compiling process is important because it clarifies how code is transformed from human-readable form into machine code. This knowledge helps in debugging and optimizing code performance.

What is the significance of creating a custom header file in a program?

Creating a custom header file allows programmers to organize and reuse code effectively. It promotes modularity and can include constants, macro definitions, and function prototypes.

How does the script demonstrate the use of a custom header file?

The script demonstrates by creating a new file named 'bies_info.h', defining constants within it, and then including this file in the main program using the '#include' directive.

What is the formula used in the script to calculate the age of girls someone is allowed to date?

The formula used in the script is to take the person's age, divide it by two, and then add seven to find the minimum age of girls they are allowed to date.

What is the practical example given in the script to utilize the custom header file and constants?

The practical example is a program that calculates the age of girls the programmer, named Bucky, is allowed to date based on his age using the formula provided and constants defined in the custom header file.

Outlines

00:00

📝 Understanding Preprocessor Directives

The first paragraph introduces the concept of preprocessor directives in programming. It explains that these directives are lines at the top of a program that perform tasks before the program compiles. The video discusses the 'include' directive, which is used to incorporate other files into the program, such as 'stdio.h' and 'stdlib.h', and how it translates to machine code. It also touches on the '#define' directive, which allows the creation of constants—variables whose values cannot change once set. The paragraph emphasizes the importance of distinguishing constants from variables by using uppercase letters and concludes with a demonstration of creating a custom header file and using a constant within it.

05:01

🔧 Creating and Utilizing Custom Header Files

The second paragraph delves into the process of creating a custom header file, named 'bies.info', and demonstrates how to include it in the main program. It explains the difference between using angle brackets and double quotes for including files, with the former searching default locations and the latter searching in the same directory. The paragraph also illustrates defining constants within the header file and using them in the main program. It provides a practical example of calculating the maximum age of girls one is allowed to date based on a formula involving the user's age. The summary includes a light-hearted conclusion about the presenter's intention to find someone who fits the calculated age criteria, emphasizing the practical application of the concepts discussed.

Keywords

💡Preprocessor Directives

Preprocessor directives are special instructions that are processed before the compilation of a program. In the video, they are used to include header files and define constants, which are essential for setting up the program's environment. An example from the script is '#include', which tells the compiler to include the contents of a specified file, such as 'stdio.h' for standard input and output functions.

💡Compiling

Compiling is the process of translating code written in a high-level language into machine code that a computer can execute. The video explains that before the actual compilation, the preprocessor directives are processed. This process is crucial as it sets up the necessary libraries and constants that the program will use.

💡Include

The 'include' directive is used to insert the content of one file into another during the preprocessing stage. In the context of the video, '#include <stdio.h>' is used to include the standard input and output library, allowing the use of functions like 'printf' for displaying output on the screen.

💡Standard Input Output (stdio.h)

Stdio.h is a standard library in C programming that provides functions for standard input and output operations. In the video, it is included using the 'include' directive, which allows the programmer to use functions like 'printf' for outputting text to the console.

💡Define

The '#define' preprocessor directive is used to define constants whose values cannot change throughout the program. In the video, the presenter uses '#define' to create a constant called 'my_name' and assigns it the value 'Tuna McButter', demonstrating how constants are declared and used in the program.

💡Constants

Constants are values that remain unchanged throughout the execution of a program. They are defined using '#define' and are typically written in uppercase to distinguish them from variables. In the video, the concept is illustrated by defining 'my_name' and 'age' as constants.

💡Header Files

Header files, usually with a '.h' extension, contain function declarations and macro definitions that can be included in multiple source files. The video demonstrates creating a custom header file named 'bies_info.h' to store constants and include it in the main program for easy access and reuse.

💡Custom Header File

A custom header file is a user-created file that includes specific declarations and definitions for use in a program. In the script, the presenter creates a header file named 'bies_info.h' to store personal constants like 'my_name' and 'age', which can then be included in the main program for convenience.

💡Macros

Macros are a way to define a piece of code that can be reused throughout a program. In the video, '#define' is used to create macros for constants. The script demonstrates how macros can simplify the code by replacing instances of 'my_name' with the string 'Tuna McButter' before compilation.

💡Compilation Process

The compilation process involves converting the source code into an executable format. The video explains that the compilation process begins after the preprocessor directives have been executed, which includes including files and defining constants that are then used in the program.

💡Age Calculation

The script includes a humorous example of calculating the age of girls the presenter is allowed to date based on his own age. This calculation demonstrates a practical application of the concepts introduced in the video, such as using constants and performing arithmetic operations in C.

Highlights

Introduction to preprocessor directives in programming.

Explanation of the 'include' directive for incorporating standard libraries.

The process of compiling a program and the role of preprocessor directives.

Demonstration of creating a custom header file for code organization.

Use of 'stdio.h' for standard input and output operations.

Introduction to the 'Define' preprocessor directive for creating constants.

Difference between variables and constants in programming.

The convention of writing constants in uppercase letters.

How the 'Define' directive replaces occurrences of a constant with its value.

Creating a new file for custom header information.

Explanation of file extensions and their significance in programming.

Inclusion of custom header files using angle brackets and double quotes.

Difference between searching default places and the same directory for header files.

Creating a program to calculate the age of girls one is allowed to date based on a formula.

Use of mathematical operators in C programming for calculations.

Incorporate custom constants into the main program for practical use.

Final program output displaying the calculated dating age limit.

Humorous conclusion encouraging viewers to find someone within the calculated age range.

Transcripts

all right guys welcome back and in this

video I'm going to be talking to you

guys about these lines at the very top

of your program and they're technically

called preprocessor

directives now you know how I told you

guys like in the first video that the

reason that we download this piece of

software is not only so we can type code

in it but also one of the jobs of this

piece of software was basically a take

code that we can understand of course we

can read this this is the word include

domain and it pretty much translates it

into ones and zeros or in other words

code the computer can understand now

this process the technical term for it

is compiling your program so what these

lines are and why I even mentioned that

is because before your program compiles

what it does is it

includes or pretty much runs your

pre-processor processor directives kind

of a tongue twister but basically it's

going to grab the entire file wherever

you tell it to so it's going to grab

stdio.h and stdlib.h and it's going to

substitute them in place right here now

after all your pre-processor directives

are finished completing then it's going

to go ahead and compile your program and

also um like this one right here this

stdi iio stands for standard input

output and and that's what allows us to

use that print F because it outputs

stuff on the screen so again what this

include does is basically include

another file with well whatever um we

want to put in it and I'll actually show

you guys how to make your own file in

just a second now another pre-processor

directive you can use other than include

is actually one called Define and I'll

show you guys how to use that right now

pretty much type in the I call it

hashtag cuz I'm stupid Twitter now but

the pound sign hit Define and what a

constant is is it's basically it's kind

of like a variable but its value can

never change so whenever you have a

variable like tuna you can set it equal

to 21 and then later on you can set it

equal to 32 well with a constant you

can't change its value you set it once

in your program and it stays that way

forever so if you want to um I don't

know just make a stupid constant just to

show you guys an examp example called my

name and also whenever you're making

constants make sure that you make them

in all uppercase letters and this is

just so you can easily distinguish a

constant from variables in your program

it's uh I don't know it's just uh like

something all programmers do so of

course type the name whatever you want

to name your constant and then after it

it's values so I'll just say my name is

tuna

mcbutter and another thing I want to

point out is that you don't need a

semicolon at the end of any

pre-processor

directive so now basically what's going

to happen is anytime we have my name in

our program might as well use

it and what are we going to put

something stupid like me name B and

we'll just

write my name right there so basically

what this pre-processed is going to do

is it's going to search your program

right here and it's going to look for

any instances of the word my name and

replace them with the string tuna

mcbutter so now if we run this it says

me name be tuna mcbutter and of course

it did all of that before your program

started compiling so now let me go ahead

and actually show you guys how to use

these in a useful kind of way so clear

this out and clear this out as

well and I want to show you guys how to

include your own customade header and we

actually use one of those constants

because why the heck not so the first

thing we need to do if we want to

include another file is well create a

new file so if you go to file new empty

file and it says do you want to edit yes

and now you pretty much just uh give it

a name I'm going to name mine

bies info and you also want to put H

it's just a header file and it's just um

I'll explain you guys about the

different types of files later on but

whenever we're including this give a a h

extension it means something special to

see so hit save and then it says okay

pretty much do you want to add it yep

and another thing I want to mention is

that whenever we named it h what it

means to see is a header files so it

creates a new folder called headers and

it organizes pretty much all your header

files for you by default which is pretty

sweet so now we have two files in our

program this first one of course is the

one main.c the main one we've been

working on the whole time and we also

have this new bies dotinfo or excuse me

bues

info. now also take note of these other

header files we include were also H so

you know in case you didn't notice that

now in this one remember what's going to

happen is any code that's in here is

pretty much be copied and substituted

right whenever we write our

pre-processed directive so we can um

write something like let's just go ahead

and Define a couple constants so

Define my name and I'll put my uh real

name this time no more that tunic butter

whatever he heck his name

is and I'll just go ahead and Define um

age 28 so now and we actually don't need

to save these because whenever we build

and run it automatically saves all your

files for you so pretty cool you can do

it the lazy way so now we have a little

bit of code in this bues info. and let's

go ahead and include it in our main

program so copy this do it the lazy

way and

also delete your entire STD lib piece of

code right now and as you can see this

header and this header are brought in

using the brackets and whenever you use

brackets it says it pretty much means uh

search the default place where headers

are but we can use double quotes and

double quotes means search in the same

um directory or the same folder is our

code and it's just a little bit faster

way to bring it in um don't really worry

about it right

now and of course type the name of your

file so again it's going to include this

one this one and then it's pretty much

going to copy this and paste it right in

here that's like pretty much what it

does actually I should probably used

that analogy earlier on and then it runs

your program so now that we have this

info brought in let's make a cool

program with it I'll show you guys how

to make a program that calculates the

age of girls I'm allowed to date so I'm

like all right am I allowed to date a

girl who's like 24 if I'm 28 well I

don't know what about a girl who's 17

probably not so you know the formula for

it is this

go ahead and make a variable called int

girls age and the formula for this is

actually um and I'm going to do some

math and I know I didn't talk to you

about the um mathematical operators of C

yet but you guys will understand this

you take the age and this is my age

which is 28 and you divide it by two of

course to divide is just uh forward

slash and I'll talk like I said talk

about that later on so now of course

this is 14 for me me and you take that

and add seven and that's the age of

girls anyone is allowed to date so go

ahead and think of your age right now

divide it by two and add seven don't

they any girls younger than that so this

should equal 21 I believe

so now let's just go ahead and add a

print statement don't need to do

anything

else so I'll just put something like um

s which would be my name like Bucky

Roberts

can date girls who

are um actually girls do this percent or

older and of course now we need to give

it those uh pretty much uh like pieces

of information it asked for and this is

what I name it age or the first one is

my

name and the second one is girls age

so let's see if this

works all right so Bucky can date girls

21 or older all right I am fine with

that got to go find me some 21y old

hottie now if anyone's listening give me

a call all right so I'll talk you guys

through this one more time real quick

just so it sticks in your brain and

you're pretty much a pro at it what we

can do is we can write our own custom

header file and any code we put in here

as our program runs it pretty much grabs

this file copies all the crap in it and

pastes it right here and then your

program compiles and in our program what

we did is we took my age divided it by

two and add seven to that value and it

gave us the girl's age that you're

allowed to date and I got 21 so I'm

going to pause this video go find some

21y old hottie and I'll see you later