Computer Programming

Terms from computer science:

You can imagine list like as string of pearls. They are connected with thread. If you got one you can go by thread to the other one next to it.

An array is like a meter. You know where you are so you can jump any amount of units around.

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Python is just a programming software, you don't actually need it to run your computer. You can use Python if you'd like to program something, or learn how to program.

You don't need if you don't want to develop computer programs. But if you want you should use it, for you can not make programs without a compiler.

Compiler is the programs that makes the computer program out of the code

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Assembler, COBOL, PL/I, C/C++ are all translated by running the source code through a compiler. This results in very efficient code that can be executed any number of times. The overhead for the translation is incurred just once, when the source is compiled; thereafter, it need only be loaded and executed.

Interpreted languages, in contrast, must be parsed, interpreted, and executed each time the program is run, thereby greatly adding to the cost of running the program. For this reason, interpreted programs are usually less efficient than compiled programs.

Some programming languages, such as REXX™ and Java™, can be either interpreted or compiled.

Storing global data.

these are difference in between c and c++: a) C is a SPL and C++ is a OOP. b) C has not concept of object but C++ has this feature. c) C has not 'class' name data type but C++ has.

When you turn it off, all memory is lost. You usually end up with pseudo-random patters.

To actively clear all mem would require a machine language program ... which would be wiped in the process.

Period is 101110

Assembly language is easier to produce as output of compiler and it is easier to debug assembly language.

The declaration of an array of 3 int pointers will be:

int *p[3];

The declaration of a function that receive an array of int pointers will be:

int my_func(int **p);

or

int my_func(int *p[]);

and you can pass it to other function simply by passing p.

#include <stdio.h>

int main()

{

int i;

for(i = 51; i <= 100; i+=2)

printf("%d\n", i);

return 0;

}

Syntax Error: error due to missing colon, semicolon, parenthesis, etc. Syntax is the way in which we construct sentences by following principles and rules.

Example: In C++, it would be a syntax error to say

int x = "five";

This will not compile because it does not follow the syntax of the language and does not make any sense to the compiler.

Semantic Error: it is a logical error. it is due to wrong logical statements. Semantics is the interpretations of and meanings derived from the sentence transmission and understanding of the message. Semantics errors are Logical, while Syntax errors are code errors.

Example: A semantic error would compile, but be incorrect logically:

const int pi = 12345;

Your program will likely compile and run without error but your results will be incorrect. (Note that these types of errors are usually much harder to debug)

Three type of languages

High level

Mid level

Low level

Arrays allow similar types of data to be stored within a contiguous block of memory such that every data element is accessible in constant time, regardless of its physical location within the array. This is achieved through simple pointer arithmetic treating each element as a memory offset from the start of the array. Since every element is the same length (in bytes), locating any element is simply a matter of calculating its offset from its index. Indices are zero-based thus the third element can be found at index 2. The memory offset for that element is therefore the product of the element size and 2. However, C permits indices to be specified directly, while the pointer arithmetic is done in the background. Thus array_name[2] automatically returns a reference to the third element.

Arrays with large and complex variable length data elements need to store those elements separately from the array, usually non-contiguously. This is achieved by using a pointer array. Pointer arrays are particularly useful when sorting extremely large data lists as it is much easier and more efficient to implement a sorting algorithm with an array than it is with a linked list, particularly when constant-time random-access is essential to the algorithm. The time and effort in building the array is generally more than compensated for by the efficiency of the algorithm.

Arrays can also be divided and subdivided to better model the data they represent. For instance, a chessboard might be implemented as a one-dimensional array of 64 elements, however it makes more sense to model the chessboard in a two-dimensional array of 8x8 elements. Although the array is still allocated contiguously and can be thought of as being 8 rows and 8 columns, it's actually better to think of this two-dimensional array as being a one-dimensional array of 8 elements, where each element is another one-dimensional array of 8 elements.

By thinking this way it makes it possible to allocate extremely large arrays in non-contiguous memory (as completely separate one-dimensional arrays) and also makes comprehension of a four-dimensional array in a three-dimensional world that much easier (unless you actually want to model time and space of course).

A four-dimensional array can be thought of in a variety of ways: as being a one dimensional array of three-dimensional arrays, or as a two-dimensional array of two-dimensional arrays, or as a three-dimensional array of one-dimensional arrays, or even as a one-dimensional array of one-dimensional arrays of one-dimensional arrays of one-dimensional arrays. Whichever method you use to imagine your array is immaterial, so long as it makes sense to you that's all that really matters.

A recursive function is one that calls upon itself until a given result in the original call is met.

Take a look at this example.

Program Recursion;

Uses

crt;

Var

number:longint;

Function Factorial(number:longint):longint;

Begin

if number > 0 then

factorial:=number*factorial(number-1)

else

factorial:=1;

End;

Begin

clrscr;

readln(number);

writeln(factorial(number));

readln;

End.

Note how the function factorial calls itself.

You really don't have to, the vast majority of computer users will never need to know any. Just like the vast majority of car drivers don't need to study auto mechanics. People that will never use a computer certainly have no need. However if you want to program computers, either for your own casual entertainment or for a job, that's why!

Raw data becomes information once it is organized and sorted. Raw data that is collected, is useless until it becomes information.