The following are concepts that you will find in almost every programming language in no given order.
Syntax
Syntax are rules which defines how keywords, identifiers and symbols are to be used to form statement which are legal in a given programming language.
A correct statement in a given language have abided to the language's syntax. Syntax error is one of the most common programming errors, it is encountered when a programmer fails to follow the language's syntax for example by misspelling keywords or failing to add necessary symbols such as a comma to separate items in an array or failing to terminate a line with a semicolon in some languages.
statement
A statement in a natural language refers to a definite expression of something in speech in the other hand a statement in a programming language expresses a syntactically correct definite unit in the given language.
You can remove a statement from a program without causing syntax error because each statement is supposed to be able to stand alone syntactically. A complete statement in a programming language is formed using keywords, identifiers and legal symbols combined together to form the smallest unit of a program which is correct in terms of syntax.
Keyword
Keywords in a programming languages are predefined words which performs a certain general action in the language. Some of common keywords across multiple languages are return, for, while , yield , continue, break and many others.
runtime
Program runtime is the time in between when the program starts running until it terminates. This is the running phase of a program. Anything which happens at the time when the instructions are being run by the computer is said to happen at the program's runtime. For example, a runtime error is an error which happens at runtime , this errors can be caused due to flaw in programs logic such as trying to divide a number by zero.
Variable
A variable is a user defined item in computer memory that is subject to change during the program's runtime.
Constant
Identifier
Function
A function is the grouping of statements which performs one coherent task such that they can be run as a block. Functions are usually given a name(identifier) to which when called executes the statements inside the function. Sometimes when this block of statements is executed , the results of the computation is sent to where the function was called. Most languages implements a special keywords usually return to send the results to the object which called the function.
Programming languages also offers a way that a function can communicate to the outside 'world' through the use of arguments. Arguments are values passed to the function when being called and they become accessible in the program's scope.
Object scope
global scope
This is usually the top level scope in a program , objects such as variables and functions in global scope are accessible to every part of a program.
local scope
Unlike global scope, objects in local scope is only accessible to the block that it exists in. The various blocks used to define objects scope are functions , conditional branches and loops. For example a variable declared inside a block such as a function or a loop is usually only accessible within that block unless it is 'forcibly' made global using some special ways unique to the language in use.
loop
counter = start
while (counter < stop):
Do something
increment counter
//where start and stop are integers
Incrementing means increasing the counter with a certain value. What happens is that as the counter is increased at each iteration the number we set as stop remains constant , this means that eventually the counter will be greater than the stop thus making the condition to fail and consequently the loop to terminate.
Branch
A branch in a program is when the program execution flow encounters conditional blocks and has to 'branch' and continue in the direction which satisfies a given condition. Conditional blocks in most languages are signaled by if block,the statements within this block are only executed if the condition it specifies is met otherwise the program flow continues ignoring the statements inside the block. Conditional blocks can be chained using the if block followed by else if blocks . The else if block is common in most programming language but some can use other terms to refer to the blocks , for example , python uses elif instead of else if . And finally the blocks can be finalized by an else block which will get executed if all the other blocks fail. The structure of conditional branching is normally like:
if (something):
do this
else if(something_else):
do this
else if(something_else):
do this
else:
do this
expression
An expression in a programming language normally looks like typical mathematical expressions. The simplest expression is a numerical value such as 6, 8, 2.5, 3.2, etc. , this type of an expression evaluates to itself.
Multiple datatype can be combined using brackets () to form compound expressions for example ( 2 * ( 3 + 2.5) ) .The results of such expressions can be assigned to variables and constants.