Computer Programming

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This section covers programming fundamentals — tokens, data types, variables, constants, operators, formatted/unformatted I/O, structured vs object-oriented programming, and algorithms & flowcharts.

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Tokens, Data Types & Variables A token is the smallest individual unit of a program — keywords, identifiers, constants, operators, and punctuation/special symbols (comments are stripped out and are NOT tokens).

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Common data types: int (integers), float/double (decimals), char (single character), void (no value).

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A variable is a named memory location whose value can change; declared as type name;

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Numeric (e.g., 25, 3.14), Character (e.g., 'A'), String (e.g., "Hello") — values that do not change during execution.

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Operators Category Examples Arithmetic + − * / % (modulus) Assignment = += −= *= /= Relational / Comparison == != < > <= >= Logical && (AND) || (OR) ! (NOT) Input & Output Statements Formatted I/O (e.g., printf()/scanf() in C): uses format specifiers — %d (int), %f (float), %c (char), %s (string).

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Unformatted I/O (e.g., getchar()/putchar(), gets()/puts()): reads/writes raw characters or strings without format conversion.

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Structured vs Object-Oriented Programming Paradigm Approach Structured programming Program organized top-down around functions/procedures that operate on separately declared data (e.g., C) Object-oriented programming (OOP) Data and the functions that operate on it are bound together into objects/classes (e.g., C++, Java) Algorithms & Flowcharts An algorithm is a finite, step-by-step procedure for solving a problem, independent of any programming language.

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A flowchart represents an algorithm graphically using standard symbols: oval (start/end), rectangle (process), diamond (decision), parallelogram (input/output).

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This section covers decision-making statements (if, if-else, switch), loop statements (for, while, do-while), and control-breaking statements (break, continue, goto).

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Decision-Making Statements Statement Behaviour if Executes a block only if the condition is true if-else Executes one block if the condition is true, another if false Nested if- else Tests multiple conditions in sequence, one inside another switch-case Selects one of several blocks to execute based on the value of a single variable/expression; typically uses break to prevent fall-through, and a default case for no match Loop Statements Loop Type Key Feature for loop Entry- controlled Combines initialization, condition, and increment/decrement in one line — ideal when the number of iterations is known while loop Entry- controlled Condition tested BEFORE each iteration — may execute zero times do-while loop Exit- controlled Condition tested AFTER each iteration — body always executes at least once Breaking Control Statements break: immediately exits the enclosing loop or switch statement. continue: skips the remaining code in the current iteration and proceeds to the next iteration of the loop. goto: performs an unconditional jump to a labeled statement; generally discouraged as it can make code harder to follow (“spaghetti code”).

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This section covers function definition and use, function prototypes, argument-passing methods, and recursive functions.

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Defining & Using Functions A function is a self-contained block of code that performs a specific task; using functions promotes modularity and code reusability.

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A function prototype declares a function's return type, name, and parameter types before it is used/defined, allowing the compiler to check calls for correctness.

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A function with no return value uses the return type void.

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Local variables declared inside a function are accessible only within that function (scope is local).

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Passing Arguments to a Function Method Behaviour Call by value A COPY of the argument's value is passed; changes inside the function do NOT affect the original variable Call by reference (pointer) The ADDRESS of the argument is passed; changes inside the function DO affect the original variable Passing an array to a function effectively passes a pointer to its first element (not a full copy) — so changes to array elements inside the function DO affect the original array.

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Recursive Functions A recursive function is one that calls itself to solve smaller instances of the same problem (e.g., factorial, Fibonacci).

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Every recursive function MUST have a base case that stops further recursive calls — without one, it will recurse indefinitely (stack overflow).

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Recursive functions typically consume more stack memory than an equivalent iterative (loop-based) solution, due to repeated function-call overhead.

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This section covers pointer declaration and arithmetic, the relationship between pointers and arrays, and dynamic memory allocation.

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Pointer Basics A pointer is a variable that stores the ADDRESS of another variable, rather than a data value directly.

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Declaration: type *ptr;

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(e.g., int *p; declares a pointer to an int).

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The & (address-of) operator returns a variable's address; the * (dereference) operator accesses the value stored at the address a pointer holds.

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Pointer Arithmetic Incrementing a pointer (ptr++) moves it forward by sizeof(pointed-to type) bytes — not necessarily 1 byte.

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Subtracting two pointers of the same type gives the NUMBER OF ELEMENTS between them (not the raw byte difference).

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Pointers & Arrays In C, an array name used in an expression generally decays into a pointer to its first element. arr[i] is equivalent to the pointer expression *(arr + i).

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Dynamic Memory Allocation Function/Keyword Purpose (Language) malloc() Allocates a block of uninitialized memory at runtime (C) calloc() Allocates and zero-initializes memory for an array of elements (C) realloc() Resizes a previously allocated memory block (C) free() Releases (deallocates) previously allocated dynamic memory (C) new / delete Allocate / deallocate memory dynamically (C++) Dynamic memory allocation lets a program request and release memory at RUNTIME, rather than fixing all memory needs at compile time — essential for data structures whose size is not known in advance.

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This section covers array definition, processing and passing to functions, multidimensional arrays, and structures — including arrays of structures and pointers to structures.

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Arrays An array is a collection of elements of the SAME data type, stored in contiguous memory locations and accessed by an index.

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Processing an array typically uses a loop to visit each element by index (e.g., for (i=0; i<n; i++)).

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When an array is passed to a function, it is passed effectively BY REFERENCE (as a pointer to its first element) — not as a full copy.

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A multidimensional array (e.g., a 2D array) can be thought of as an array of arrays — commonly used to represent matrices and tables of data.

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Structures A structure (struct) is a user-defined data type that groups variables of DIFFERENT data types under a single name — unlike an array, which holds only one data type.

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Structure members can be initialized at the time of declaration using an initializer list.

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Concept Description Array of structures A collection of structure variables (records), each sharing the same layout — e.g., a list of student records Pointer to structure A pointer that holds the address of a structure variable; members are accessed using the -> (arrow) operator Structure members are accessed directly with the .

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(dot) operator; through a pointer, with the -> (arrow) operator.

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This section covers key object-oriented programming features: inline functions, function overloading, classes and objects, member functions, static members, operator overloading, inheritance and polymorphism.

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Classes & Objects A class is a blueprint/template that defines data members and member functions; an object is a concrete INSTANCE of a class.

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Access specifiers control visibility of members: private (accessible only within the class's own member functions, by default), public (accessible from anywhere), protected (accessible within the class and its derived classes).

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A private member function can be called only from within the class's own member functions, not directly from outside code.

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A constructor is a special member function used to initialize an object automatically when it is created.

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Inline Functions & Function Overloading An inline function is expanded directly at the point of call (avoiding function-call overhead) — suitable for small, frequently used functions.

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Function overloading allows multiple functions to share the same name but differ in their parameter list (number/type of parameters) — a form of compile-time polymorphism.

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Static Data Members & Static Member Functions Feature Behaviour Static data member A SINGLE copy is shared among ALL objects of the class (not unique per object) Static member function Can be called WITHOUT creating an object of the class; can only directly access other static members Operator Overloading, Inheritance & Polymorphism Operator overloading lets a programmer redefine how existing operators (e.g., +, ==) behave for user- defined (class) types — it cannot be used to invent entirely new operators.

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Inheritance allows a derived (child) class to acquire the properties and behaviours of a base (parent) class, promoting code reuse and establishing an “is-a” relationship.

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Polymorphism is the ability of a function or object to take multiple forms — achieved at COMPILE time via overloading, or at RUN time via overriding/virtual functions.