Are you starting your journey into the world of programming? Whether you are aiming to write low-level system kernels or high-performance applications, understanding the foundational differences and similarities between C and C++ is crucial.
This guide breaks down the core building blocks of these languages: variables, constants, operators, and the essential input/output (I/O) mechanisms.
1. The Legacy: C vs. C++
Before diving into code, it is helpful to understand the lineage of these tools.
- C (1972): Created by Dennis Ritchie and Brian Kernighan, C is known for being simple, minimal, and providing fast, low-level memory access. It was the language used to write the UNIX operating system.
- C++ (1983): Developed by Bjarne Stroustrup, C++ builds upon C by adding object-oriented programming features while remaining mostly compatible with C.
2. Basic Types
Signed Integer
| Type | Size | Range |
| char | 1 byte | -128 .. 127 |
| short | 2 bytes | –32 768 .. +32 767 |
| int | 2 bytes* 4 bytes* | –32 768 .. +32 767 –2 147 483 648 .. +2 147 483 647 |
| long | 4 bytes | –2 147 483 648 .. +2 147 483 647 |
| long long | 8 bytes | –9 223 372 036 854 775 808 .. 9 223 372 036 854 775 807 |
Unsigned Integer
| Type | Size | Range |
| unsigned char | 1 byte | 0 .. 255 |
| unsigned short | 2 bytes | 0 .. 65535 |
| unsigned int | 2 bytes* 4 bytes* | 0 .. 65535 0 .. 4 294 967 295 |
| unsigned long | 4 bytes | 0 .. 4 294 967 295 |
| unsigned long long | 8 bytes | 0 .. 18 446 744 073 709 551 615 |
*Dependent on the computer architecture.
Floating Point
| Type | Size | Range |
| float | 4 bytes | 3.4E +- 1038 (7 digits) |
| double | 8 bytes | 1.7E +- 10308 (15 digits) |
Boolean
| Type | Size | Value |
| bool | 1 byte | true/false |
Standard Integer
Library: <stdint.h> (C) or <cstdint> (C++)
It is not system/platform dependent.
| Type | Size |
| int8_t, uint8_t | 1 byte |
| int16_t, uint16_t | 2 bytes |
| int32_t, uint32_t | 4 bytes |
| int64_t, uint64_t | 8 bytes |
Character
| Character | Code |
| ‘ ‘ (Space) | 32 |
| ‘0’ .. ‘9’ | 48 .. 57 |
| ‘A’ .. ‘Z’ | 65 .. 90 |
| ‘a’ .. ‘z’ | 98 .. 122 |
Wide Character
Store UTF-16 or UTF-32
| Type | Size |
| wchar_t | 2 bytes (Windows) 4 bytes (Linux) |
| char8_t | 1 byte |
| char16_t | 2 bytes |
| char32_t | 4 bytes |
3. Variables and Constants: Storing Data
Variables
A variable is a name given by the programmer to a specific memory region (RAM) used to store a value. Every variable must have a specific data type, which dictates the size of memory allocated and the range of values it can hold.
Syntax for Declaration:
// Explicit type declaration
int age = 12;
float final_score = 9.5f;
// Type inference (C++11 and later)
auto length = 18.6;Naming Rules: When naming variables, remember to use characters a-z, A-Z, 0-9, or underscores (_). Names cannot begin with a digit and must avoid reserved keywords like int or float.
Constants
Constants are similar to variables but store values that cannot be changed during the program’s execution.
How to Define Constants:
- Macro (Legacy C):
#define PI 3.14159 - Const Keyword:
const int MAX_SIZE = 100; - Constexpr (Modern C++):
constexpr uint16_t BUFF_SIZE = 1024 * 4;
Tip: By convention, constant names are written in ALL CAPS (e.g., MAX_SIZE) to distinguish them from variables.
4. Operators: Performing Calculations
C/C++ provides a rich set of operators to manipulate data.
Unary Operators: Act on a single operand.
a++(Post-increment): Uses the current value, then increases it.++a(Pre-increment): Increases the value, then uses it.
Binary Operators: Act on two operands.
- Standard math:
+,-,*,/ - Modulus (Remainder):
%(e.g.,5 % 2results in1) - Comparison:
>,<,==,!=(Returnstrueorfalse) - Logical:
&&(AND),||(OR)
Ternary Operator: A shorthand for if-else.
- Syntax:
<condition> ? <true_value> : <false_value> - Example:
max = (a > b) ? a : b;
Additionally, there are many other operators that you can explore by visiting the following website.
5. Input & Output: Talking to the User
This is where C and C++ diverge significantly in syntax, though the logic remains the same: Input → Processing → Output.
The C Way: stdio.h
C uses the <stdio.h> library with specific format specifiers to manage data types.
printf("Hello %s.\n", name);
// %d for integers, %f for floats, %s for strings
scanf("%f", &math_score);
// Note: You must typically use the address-of operator (&) for variables.Formatting: You can control precision easily, e.g., %7.3f prints a float with a width of 7 and 3 decimal places.
The C++ Way: iostream
C++ introduces streams via <iostream>, which are generally easier for beginners as they handle data types automatically.
std::cout << "Name = " << name;
std::cin >> math >> lit;Formatting: Requires <iomanip>. You can use manipulators like setw(width) to format output tables nicely.