updated 28 May 2023
TOC
Of all the inventions in the field of electronics like the radio and telephone, the programmable computer was the most significant one. It changed the world forever.
If ever a certain device can be programmed the way we want it to behave, then we can simply instruct it to do things for us. That's very practical, isn't it?
After the programmable computers, the next big question was how humans would program these computers. They began developing programming languages and the 1970s was a very remarkable period: the C language was invented.
After the success, the great potential was unleashed and we are now seeing the things a programmable computer can do: the era of information, real-time data, almost realistic 3D games, artificial intelligence, etc.
Learning computer science now is a very sophisticated one unlike it was in the past: there are too many fields even in software development alone.
And if you are a beginner, you might be discouraged from all the things you need to learn but don't worry: you don't need to learn them all. What you need to learn first is the understanding how computers work and the fundamentals of computer programming that all computer programming languages have in common.
And since almost every programming language nowadays directly and indirectly inherits concepts from the C language, we'll be using it to demonstrate the core concepts of programming.
Take note: we don't want to discuss every detail of the code in terms of the C language, rather we just want to get the core concepts of computer programming that are common in different programming languages.
As was mentioned, a programmable computer is very important but the way you interact with the computer is through input and output: you as the user will have an input, the computer will process it (the way it is processed is programmed also), then the computer will output something. The very first demonstration is the "Hello World" program. The programmer will tell the computer to simply display the message on the screen.
But of course, complex programs are not as straightforward as that. Typical programs like binary to human language (and vice versa) takes a lot of processing, an operating system to recognize computer applications, a business collaborative tool with a lot of features to manage data, a 3D game that is almost realistic, an Artificial Intelligence program that can simulate humans in the virtual world!
But of all the things programmers can do, the computer only processes input as binary data (0s and 1s) and it should not be interpreted literally. It's just a representation of something a computer can recognize: absence or presence of electric pulse. Compare this with any drawing that can be accomplished just by simply using a dot-and-no-dot pattern! It's the same thing for the computer.
#include <stdio.h>
int main() {
printf("Hello World!\n");
printf("Life is a blessing!\n");
return 0;
}
In this small program, the #include
tells the computer to include a certain
source which is needed because
it contains the predefined command printf.
printf simply tells the computer
to display the text provided by the programmer.
As simple as that, you have now the complete idea of what a programmable computer is all about. It's you telling the computer to do things it can handle in terms of binary data.
In computer programming, a variable is just like a container to store digital data. A data type is the way you tell the computer how that data will be interpreted. Should the computer interpret that as letters? or numbers? or words? or simply raw binary data? The computer does not know that, you must tell it exactly.
In computer programming, both these things
will enable you to store data and tell
the computer what kind of data it is. When you
store, you want to retrieve it later as per
needed. Remember also, computer's memory
is different from storage. Think of it
as the short-term memory and the storage
(the hard disk) as the long-term memory.
But during the runtime of a program you
are developing, you refer to memory as
storage. The computer's memory has the full
access to the CPU while the disk does not have
that access.
In order to read contents from the hard disk,
a request should be made. Hence, in programming
you are using the memory first not the disk.
There is the current development to combine
the two but is still on-going.
Take note, the details of memory, hard disk and CPU are quite complex but the mentioned details above will serve as the starting point for full comprehension.
#include <stdio.h>
int main() {
int i = 1;
char myletter[] = "myletter";
float x = 1.23;
printf("int i: %d\n", i);
printf("char myletter[]: %s\n", myletter);
printf("float x: %f\n", x);
return 0;
}
In this simple program, we declare and assign 3 variables with different data types:
- variable
ithat contains 1 numeric value - variable character
myletter[]that contains lettersmyletter - variable
xthat contains 1.23 value
After that, the program is telling the computer to display these values.
In programming just like in mathematics, there are operators and the most common in computer programming are assignment, arithmetic and comparison operators.
#include <stdio.h>
int main() {
int c;
c = 10;
printf("c = %d\n", c);
c = 15;
printf("c = %d\n", c);
c = 3;
printf("c = %d\n", c);
return 0;
}
The most common assignment operator is
= and it should not be confused with
the double == comparison operator.
This time, it is simply assigning a value to a variable. The result is:
c = 10
c = 15
c = 3
Variable c contains a value at a specific time.
It was changed in the program three times.
#include <stdio.h>
int main() {
int a = 10;
int b = 5;
int result;
printf("where a = %d & b = %d \n", a, b);
result = a + b;
printf("a+b = %d \n", result);
result = a - b;
printf("a-b = %d \n", result);
result = a * b;
printf("a*b = %d \n", result);
result = a / b;
printf("a/b = %d \n", result);
return 0;
}
Since these are arithmetic operators, they will do the basic arithmetic operations.
The result is:
where a = 10 & b = 5
a+b = 15
a-b = 5
a*b = 50
a/b = 2
#include <stdio.h>
int main() {
int a = 10, b = 10, c = 20;
printf("%d == %d is %d \n", a, b, a == b);
printf("%d == %d is %d \n", a, c, a == c);
printf("%d > %d is %d \n", a, b, a > b);
return 0;
}
Since these are comparison operators, they are comparing the left and right side values.
The result is:
10 == 10 is 1
10 == 20 is 0
10 > 10 is 0
The result is either 0 or 1 and remember, 0 is FALSE and 1 is TRUE.
In a comprehensive program, the computer must decide based on the condition/s given. Of course, the computer cannot do that alone, you must instruct it exactly. The most common is the IF statement with the extended IF/ELSE.
#include <stdio.h>
int main() {
int i = 10;
if (i == 10) printf("Expected value is the same as variable i, so the result is TRUE. \n");
return 0;
}
In a single IF statement, the programmer wants to test,
expect or verify something, such as this program.
The programmer is expecting that i variable
has the value 10, and variable i has the same
value, so the statement
Expected value is the same as variable i, so the result is TRUE.
will be printed. If the expected value is
not the same as the value of the variable,
the statement will not be printed.
Sometimes, just an IF will not be sufficient, particularly when you want to catch the FALSE result or create a nested IF-ELSE. So, you want to extend it and catch the FALSE result.
#include <stdio.h>
int main() {
int i = 10;
if (i == 11) {
printf("Expected value is the same as variable i, so the result is TRUE. \n");
} else {
printf("Expected value is not the same as variable i, so the result is FALSE. \n");
}
return 0;
}
Not only the statement in the ELSE branch will be printed, you can do a lot of things just like correct an error, go to a certain part of a program, etc. That's the power of catching the FALSE result.
There are commands or portions of your program to be repeated several times. Loops are there to do that. Now, there are simple loops and loops based on a given condition, much like a repeated IF statement. Simple loops are like repeat 10 times or repeat forever. Conditional loops are loops with specific conditions other than simple iteration just like in robot programming: repeat until color red, repeat until the distance is less than 50mm, etc.
The most common that we see in computer
programming: the for loop,
while loop and do-while loop.
#include <stdio.h>
int main() {
int n = 11;
int i;
int x[n];
printf("the `for` loop: \n");
for (i = 1; i < n; i++) {
printf("iteration: %d | Hello World. \n", i);
}
int y = 0;
printf("------ \n");
printf("the `while` loop: \n");
while (y < 10) {
y += 1;
printf("iteration: %d | Hello World. \n", y);
}
y = 0;
printf("------ \n");
printf("the `do while` loop: \n");
do {
y += 1;
printf("iteration: %d | Hello World. \n", y);
}
while (y < 10);
return 0;
}
the result:
the `for` loop:
iteration: 1 | Hello World.
iteration: 2 | Hello World.
iteration: 3 | Hello World.
iteration: 4 | Hello World.
iteration: 5 | Hello World.
iteration: 6 | Hello World.
iteration: 7 | Hello World.
iteration: 8 | Hello World.
iteration: 9 | Hello World.
iteration: 10 | Hello World.
------
the `while` loop:
iteration: 1 | Hello World.
iteration: 2 | Hello World.
iteration: 3 | Hello World.
iteration: 4 | Hello World.
iteration: 5 | Hello World.
iteration: 6 | Hello World.
iteration: 7 | Hello World.
iteration: 8 | Hello World.
iteration: 9 | Hello World.
iteration: 10 | Hello World.
------
the `do while` loop:
iteration: 1 | Hello World.
iteration: 2 | Hello World.
iteration: 3 | Hello World.
iteration: 4 | Hello World.
iteration: 5 | Hello World.
iteration: 6 | Hello World.
iteration: 7 | Hello World.
iteration: 8 | Hello World.
iteration: 9 | Hello World.
iteration: 10 | Hello World.
As you can see here, it's just printing the
Hello World ten times, whether it's for loop,
while loop or do-while loop.
A function is a group of statements (commands) that together perform a task. There are built-in functions and functions that a programmer will create according to his/her needs.
#include <stdio.h>
void myFunction() {
printf("Hello World.\n");
printf("Life is beautiful.\n");
printf("Cherish every single moment.\n");
}
int main() {
myFunction();
return 0;
}
The function printFunctionTest() is created by
declaring void first. Other functions will return values
but for the sake of simplicity we create a void function.
A void function will simply execute the commands
contained in it, nothing else.
Then inside the main function, you simply invoke it by its name. And all the commands inside that function will be executed line by line.
Why use functions? Imagine if there is none. Complex programs are usually composed of thousands of lines of code up to million, without any grouping, that will be very hard to handle.
If a function is generic and can be used for other projects, you can simply separate it for distribution. So your code is now reusable.