A flowchart in C represents the sequence of logical steps that a C program will implement. It uses simple shapes for actions, decisions, input and output, with arrows showing the possible routes. Programmers can plan and review a flowchart before coding to make those routes explicit. The seven examples below cover output, arithmetic, decisions, loops and a conceptual controller; each needs a trace as well as a drawing.
Seven flowchart examples for C
A flowchart helps you analyze, design and document a program. It can reveal an omitted branch or a loop that does not progress, but a diagram does not automatically validate the implementation. Use consistent input, output and decision symbols so readers can distinguish a calculation from a question.
These examples assume valid inputs in the stated domain. When implementing them, also handle failed input conversion and values outside the range of the chosen C data types.
1) Print message "Hello Everybody"
To display “Hello Everybody...”, begin at Start, follow the output shape and finish at End. A C implementation can use puts("Hello Everybody..."); with <stdio.h>. This path has no input or branch; the expected result is one displayed line.
2) Input 2 numbers from the user and print their sum
Read the first number into a and the second into b, calculate sum = a + b, then output sum. Keep the two input variables distinct. For a = 7 and b = 5, the result is 12; for -3 and 3, it is 0. Use values whose sum fits the selected data type.
3) Check whether an integer is even or odd
Read one integer num, then test num % 2 == 0. Follow Yes to “Even” or No to “Odd”; both output paths go directly to End. The two outputs are alternatives, so the Even path must not continue through Odd. Test 8, 7 and 0: the expected results are Even, Odd and Even. A yes/no branch should make that exclusive choice clear.
4) Flowchart to find the sum of the first 50 natural numbers
The next diagram accumulates the numbers from 1 through 50. Its loop should add each number exactly once and exit after adding 50. The expected total is 1275.
Initialize sum = 0 and n = 0. Increment n, add it to sum, and test whether n == 50. If not, return to the increment; otherwise print the sum. In C, equality uses ==, while = assigns a value. The equivalent loop is:
int sum = 0;
for (int n = 1; n <= 50; ++n) {
sum += n;
}
/* sum is 1275 */5) Find the factorial of a non-negative integer
For a non-negative integer n, initialize i = 1 and fact = 1. While i < n, increment i and multiply fact by i, then return to the condition. Only the No branch outputs the result and ends. For n = 0 or 1, the loop runs zero times and the result is 1; for 5, it is 120. Reject negative input and check for multiplication overflow before using this with larger values.
6) Trace a conceptual toaster controller
The main routine waits for the start button, calls Cook when pressed, then returns to checking the switch. Cook turns the heater on and reads the toast temperature. If the temperature is below the desired value, it reads again; once the value reaches or exceeds the target, it turns the heater off and returns. For a target of 80 and readings 60, 70, 80, the heat switches off at the third reading. This is a conceptual exercise: it omits timeouts, sensor faults and physical safety controls needed by a real appliance.
7) Calculation of the average of two numbers
Read two numbers and calculate their sum divided by two, then display the average. The mathematical diagram leaves the data type unspecified. In C, (num1 + num2) / 2 truncates if both operands are integers. For small inputs such as 3 and 4, ((double)num1 + (double)num2) / 2.0 gives 3.5. The GNU C manual explains integer division and remainder; choose numeric types and ranges deliberately rather than assuming the diagram supplies them.
Guidelines for Developing Flowcharts
These are some points to keep in mind while developing a flowchart −
- Make the entry and all exits explicit. A single Start and End works well for these small examples, but one exit is not a universal rule.
- Label on-page connectors consistently so each continuation is easy to find.
- For an off-page connector, identify the destination page or diagram; letters and numbers are conventions, not mandatory alphabets.
- Keep the main flow top to bottom or left to right, and mark loop-back arrows clearly.
- Avoid crossing arrows where possible. Label decision routes and trace boundary inputs before translating the diagram into code.
Create a simple flowchart online with Mockitt
For a complex program, break the review into smaller procedures rather than trying to fit every detail into one diagram. In Mockitt, arrange the relevant actions and labeled connectors, then share the logic for a colleague to trace. A drawing supports that review; it is not a C compiler.
For a focused example, put num = 8 beside the parity diagram and trace only the Yes route to “Even.” Then try num = 7 and follow No to “Odd.” This keeps the condition, its two alternatives and the expected results visible in one review scene.
Use a short label for each shape and keep the input domain beside the diagram. The historical Mockitt workspace image illustrates the editing environment; the parity scene focuses on the exercise logic.
After feedback, update the affected labels and connections, retrace both branches and test the C implementation separately. For loops, include an input that skips the loop, one that runs once and a small input that runs several times.
