![]() ![]() It is called variable because you can change the value stored. A variable is used to store a piece of data for processing. Variables and Types VariablesĬomputer programs manipulate (or process) data. In almost all of the C programs, we use #include to include the input/output stream library header into our program, so as to use the IO library function to carry out input/output operations (such as printf() and scanf()). #define PI 3.14159265 // To substitute the term PI with 3.14159265 in this file // DO NOT terminate preprocessor directive with a semi-colon #include // To include the Math library header #include // To include the IO library header Preprocessor directives are not programming statements, and therefore should NOT be terminated with a semi-colon. (Why not ends with a period like an english sentence? This is because period crashes with decimal point - it is hard for the dumb computer to differentiate between period and decimal point!)įor examples, // Each of the following lines is a programming statement, which ends with a semi-colon ( )īlock: A block (or a compound statement) is a group of statements surrounded by braces Ĭ source code is preprocessed before it is compiled into object code (as illustrated).Ī preprocessor directive, which begins with a # sign (such as #include, #define), tells the preprocessor to perform a certain action (such as including a header file, or performing text replacement), before compiling the source code into object code. A programming statement must be terminated by a semi-colon ( ), just like an English sentence ends with a period. It performs a piece of programming action. Statement: A programming statement is the smallest independent unit in a program, just like a sentence in the English language. During program development, instead of deleting a chunk of statements permanently, you could comment-out these statements so that you could get them back later, if needed. ![]() You should use comments liberally to explain and document your codes. End-of-line Comment: begins with // and lasts till the end of the current line.Multi-line Comment: begins with a /* and ends with a */, and can span several lines.Comments are not programming statements and are ignored by the compiler, but they VERY IMPORTANT for providing documentation and explanation for others to understand your program (and also for yourself three days later). Printf("The absolute difference is %d.\n", absDiff) Ĭomments are used to document and explain your codes and program logic. Printf("The sum of even numbers is %d.\n", sumEven) Printf("The sum of odd numbers is %d.\n", sumOdd) Scanf("%d", &upperbound) // Use %d to read an int // Use a while-loop to repeatedly add 1, 2, 3., to the upperbound Int absDiff // The absolute difference between the two sums // Prompt user for an upperbound Int upperbound // Sum from 1 to this upperbound Int sumEven = 0 // For accumulating even numbers, init to 0 Int sumOdd = 0 // For accumulating odd numbers, init to 0 * Sum the odd and even numbers, respectively, from 1 to a given upperbound. ![]() Read " Introduction to Programming in C for Novices and First-time Programmers" if you need help in understanding this program. C")īelow is a simple C program that illustrates the important programming constructs ( sequential flow, while-loop, and if-else) and input/output. K&R C: Pre-standardized C, based on Brian Kernighan and Dennis Ritchie (K&R) "The C Programming Language" 1978 book. ![]() Otherwise, read " Introduction to Programming in C for Novices and First-time Programmers". I assume that you could write some simple programs. Here is the declaration for isupper() and tolower() function.This chapter explains the features, technical details and syntaxes of the C programming language. If passed character(c) is uppercase, it returns lowercase equivalent to c, otherwise c remain unchanged.įunctions isupper and tolower are defined in ctype.h header file. It returns a non zero value(true) for uppercase otherwise zero(false).įunction tolower converts uppercase alphabets to lowercase. Printf("String with all lowercase characters \n%s ",Ĭ program to convert uppercase to lowercase using isupper and tolower functionįunction isupper check whether the passed character is uppercase letter or not. ![]()
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