Write a program to declare one integer variable and give it an appropriate value using scanf(). You are required to print the number and the result when the result is compared with 5 by using == and ! ==
Answers
Answer:
Step 1: Write the Source Code: Enter the following source codes using a programming text editor (such as NotePad++ for Windows or gEdit for UNIX/Linux/Mac) or an Interactive Development Environment (IDE) (such as CodeBlocks, Eclipse, NetBeans or MS Visual Studio - Read the respective "How-To" article on how to install and get started with these IDEs).
Do not enter the line numbers (on the left panel), which were added to help in the explanation. Save the source file as "Hello.c". A C source file should be saved with a file extension of ".c". You should choose a filename which reflects the purpose of the program.
* First C program that says Hello (Hello.c)
*/
#include <stdio.h> // Needed to perform IO operations
int main() { // Program entry point
printf("Hello, world!\n"); // Says Hello
return 0; // Terminate main()
} // End of main()
Step 2: Build the Executable Code: Compile and Link (aka Build) the source code "Hello.c" into executable code ("Hello.exe" in Windows or "Hello" in UNIX/Linux/Mac).
On IDE (such as CodeBlocks), push the "Build" button.
On Text editor with the GNU GCC compiler, start a CMD Shell (Windows) or Terminal (Mac, Linux) and issue these commands:
// Windows (CMD shell) - Build "Hello.c" into "Hello.exe"
> gcc -o Hello.exe Hello.c
// UNIX/Linux/Mac (Bash shell) - Build "Hello.c" into "Hello"
$ gcc -o Hello Hello.c
where gcc is the name of GCC C compiler; -o option specifies the output filename ("Hello.exe" for Windows or "Hello" for UNIX/Linux/Mac); "Hello.c" is the input source file.
Step 3: Run the Executable Code: Execute (Run) the program.
On IDE (such as CodeBlocks), push the "Run" button.
On Text Editor with GNU GCC compiler, issue these command from CMD Shell (Windows) or Terminal (UNIX/Linux/Mac):
// Windows (CMD shell) - Run "Hello.exe" (.exe is optional)
> Hello
Hello, world!
// UNIX/Linux/Mac (Bash shell) - Run "Hello" (./ denotes the current directory)
$ ./Hello
Hello, world!
Brief Explanation of the Program
/* ...... */
// ... until the end of the line
These are called comments. Comments are NOT executable and are ignored by the compiler. But they provide useful explanation and documentation to your readers (and to yourself three days later). There are two kinds of comments:
Multi-line Comment: begins with /* and ends with */. It may span more than one lines (as in Lines 1-3).
End-of-line Comment: begins with // and lasts until the end of the current line (as in Lines 4, 6, 7, 8, and 9).
#include <stdio.h>
The "#include" is called a preprocessor directive. A preprocessor directive begins with a # sign, and is processed before compilation. The directive "#include <stdio.h>" tells the preprocessor to include the "stdio.h" header file to support input/output operations. This line shall be present in all our programs. I will explain its meaning later.
int main() { ...... }
defines the so-called main() function. The main() function is the entry point of program execution. main() is required to return an int (integer).
printf("Hello, world!\n");
We invoke the function printf() to print the string "Hello, world!" followed by a newline (\n) to the console. The newline (\n) brings the cursor to the beginning of the next line.
return 0;
terminates the main() function and returns a value of 0 to the operating system. Typically, return value of 0 signals normal termination; whereas value of non-zero (usually 1) signals abnormal termination. This line is optional. C compiler will implicitly insert a "return 0;" to the end of the main() function.