1. Last week: We talked about: History of C Compiler for C programming
C applications
Anatomy of a C program

2. Running your code: How to run your C code?
First save your code in your machine using a “.c” extension.
For example, you can call your “hello world” program hello.c
Then use your C compiler to convert human-readable code to machine-readable code
gcc hello.c -o hello
The above command tells gcc to compile hello.c into a form that machine can execute.
“-o” tells it to name the compiled program 'hello'
The above command will create a hello.exe file if you are using windows.
If your code is error-free(more in next slides), you can then execute your code in the command prompt window.

3. Running your code: cont'd
To execute your hello.exe in windows machine..
Just type “hello” in the command prompt window.
The output looks something similar to this one:
IMP note:
Please make sure that your current working directory in command prompt window is the same one where your C program is saved.
Running a C code on Linux/Mac will follow very similar steps. Only few tweaks are needed.
For example, terminal should be used in Linux instead of cmd.

4. Various Error in C
Compile Error
Runtime
Syntax
Logical

5. Compile or Syntax Errors
Refers to a state when a compiler fails to compile a piece of computer program source code, either due to errors in code, or, more unusually, due to errors in the compiler itself.
A compilation error message often helps programmers debugging the source code for possible errors
Code:
Error message:
#include <stdio.h>
/* To shorten example, not using argp */
int main() {
printf ("Hello, world!\n")
return 0; }
semicolon.c: In function `main':
somefile.cpp:24: parse error before `return'
In this example: a semicolon (;) at the end of the line printf is missing. Adding a semicolon will get rid of this error.

6. Runtime Errors
Runtime errors occur when the program is running, and thus, they can only occur if there is a program to run (i.e., it must have compiled and linked without errors).
When you run the executable and something goes wrong then we call it a run-time error.
Code:
Error message:
int points = 95;
int iter = 0;
int avg;
avg = points / iter;
The program would crash saying:
Floating exception
Here, we tried to divide points with iter(=0)

7. Logical Errors Logical Error
This is an error that the programmer injected into the program
No error Is given the program will yield incorrect output

8. Programming Style Bad Coding: Good Coding:
“There is no programming language, no matter how structured, that will prevent programmers from making bad programs.” ~ Larry Flon
A working but uncommented program is like a time bomb waiting to explode.
Code that looks obvious to a programmer as he writes it is often confusing and cryptic when he revisits it a week later.
The comment starts with /*
The comment ends with */
So, please make a habit of commenting your code wherever necessary.
Only one rule exists for good programming: Make your program clear, concise and simple as possible.
Bad Coding:
Good Coding:

9. Elements of a Program Variables: Instructions Data (variables)
In computer programming, you need two things:
Data (variables)
Instructions (Code)
Variables:
Variables are the basic building blocks of a program.
We must order our materials before we start constructing a building. Similarly, we must declare our variables before we can use them.
C allows us to store values in variables.
Each variable has a variable type.
Variables are case sensitive.
Also, you can not use reserved words for variable names.
Such as, int, while, for, float …
Instructions
Instructions tell the computer what to do with the variables.

10. Variable types: int - numerical value
char - alpha/numeric character array
double – precision no less than a float ( roughly double the size of a float, refer to IEEE 754 standard or refer to float.h)
float – precision is not less than a double
Pointer (int, double, char) – a memory location

11. Integer Variables
An int variable can store a value in the range of to
Think of an int variable as no fractional parts are allowed.
Declare an int you can use the following;
int x;
int x = 10;
Note the “=“ symbol is use for assignment operations

12. Double and Floats Variables
Float, of floating point, number has about seven digits of precision and a range of about 1.E-36 to 1.E+36. A floats takes four bytes to store
Double, of double precision, number has about 13 digits of precision and a range of about 1..E-303 to 1.E A double takes eight bytes to store.
float x;
double y;
float x = 10.0;
double y = 2.567;

13. Character Variables C only has the concept of numbers and characters.
A character of ‘A’ != ‘a’, as these values refer to ASCII values
A character is a single character stored in one byte
char c; or char c = ‘X’..
Difference between “X” and ‘X’
‘X’ – means a character of 1 byte long containing the value ‘X’
“X” – s string with a length of 2 bytes containing the value “X”

14. Data types:

15. Variable nomenclature:
Characters Allowed :
Underscore(_)
Capital Letters ( A – Z )
Small Letters ( a – z )
Digits ( 0 – 9 )
Blanks & Commas are not allowed
No Special Symbols other than underscore(_) are allowed
First Character should be alphabet or Underscore
Variable name Should not be Reserved Word (int, for, if,... etc)
Valid names
Invalid names
Num1
_NUM
iNt
num 1
1num
int