### Programming Producing a set of instructions and/or data to achieve a task. **Operating System** The interface between the user and the computer hardware. - Execute user programs - Ensures programs are executed correctly - Schedules access to limited hardware resources - Makes the computer system convenient > [!NOTE] Linux OS > - UNIX-based operating system > - Open-source, lightweight, secure **Terminal** Sends text-based commands to the shell. The terminal handles user input, renders shell output. **Shell** A program that executes commands, and has its own syntax. It returns output which the terminal can display. **Prompt** Controlled by the shell, and is the line of text which displays some information. `z5585663@vx22:~$` >[!EXAMPLE] Terminal Commands >- `ls` - List files in directory >- `mkdir ` - Makes a new directory >- `cd ` - Move into specified directory >- `cd ..` - Moves up one directory level >- `pwd` - Print working directory; the current directory >- `cp ` - Copy a file from source to destination >- `mv ` - Move a file from source to destination (or rename file) >- `rm ` - Remove (delete) a file >- `touch ` - Add a file >- `clear` - Clear the terminal >- `code ` - Open file in Visual Studio Code >- `date` - Current time and date >- `echo <"string">` - Prints back the string in the quotes >- `cat ` - Prints the contents of the file >- `rquota` - Shows how much of the allotted file system storage has been used >[!TIP] Recursive Flag >`-r` flag can be added to `cp` or `mv` to recursively perform a command on all files in a directory. E.g. `cp -r ` ### Printing Printing to console using Standard Input Output library. ```c #include int main(void) { printf("Hello World!\n"); return 0; } ``` ### Compiler Compiling and running program using `dcc` compiler. >[!INFO] Compiling converts human code into machine code. ```shell # Compile program dcc program.c -o program # Run program ./program ``` ### Memory Types of memory and storing data in variables. **Types of Data Storage** - Persistent storage - HDD/SSD - Volatile memory - RAM ```mermaid graph TD; A[RAM]-->B[Stack]; A-->C[Heap]; ``` Stack is made up of a grid of 0s and 1s. ### Variables Variables provide a label for a piece of memory > [!INFO] Values of variables can change after they have been assigned. - Values of variables can change - Stores a specific type of data - Certain number of bits required to store that data type Variables require both a `name` and a `type` to be defined. > [!TIP] Variable naming conventions >- Names must be lowercase >- Words must be separated with underscores **Data Types** Bits and bytes values are the memory requirements in C. > [!INFO] `int` > - Whole integer numbers, positive or negative > - Uses 32 bits, 4 bytes > - Gives exactly 2 different possible values > - Exact ranges from -2,147,483,648 to 2,147,483,648 > **E.g.** -2, 0, 1 > [!INFO] `char` > - Single character, wrapped in **single** quotes > - Each char is associated with an integer > - Uses 8 bits, 1 byte > - Exact ranges from -128 to 127 chars > **E.g.** 'a', 'A', ' ', '1' > [!INFO] `double` > - Floating point number > - Uses 64 bits, 4 bytes > - Double the size of integers, hence called double > - Exact ranges from -2,147,483,648 to 2,147,483,648 > **E.g.** 3.14159... **Variables Syntax** Declare a variable with ` ;` ```c int age; char first_initial; double pi; ``` ```c #include int main(void) { double temperature = 19.0; double humidity = 99.5; printf("Temperature is %lf, and humidity is %lf.", temperature, humidity); return 0; } ``` > [!EXAMPLE] Format strings > - `%c` - chars > - `%d` - integers > - `%lf` - long floating point > - `%.2lf` - long floating point restricted to 2 decimals

COMP1511