Here is an example of a simple calculator program written in C language:

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#include <stdio.h> int main() {    double num1, num2;    char operator;    printf("Enter an operator (+, -, *, /): ");    scanf("%c", &operator);    printf("Enter two operands: ");    scanf("%lf %lf", &num1, &num2);    switch(operator) {        case '+':            printf("%.1lf + %.1lf = %.1lf", num1, num2, num1 + num2);            break;        case '-':            printf("%.1lf - %.1lf = %.1lf", num1, num2, num1 - num2);            break;        case '*':            printf("%.1lf * %.1lf = %.1lf", num1, num2, num1 * num2);            break;        case '/':            printf("%.1lf / %.1lf = %.1lf", num1, num2, num1 / num2);            break;        // operator doesn't match any case constant        default:            printf("Error! operator is not correct");    }        return 0; }

This program prompts the user to enter an operator (one of +, -, *, or /) and two operands. It then performs the specified operation and prints the result to the screen. The program uses a switch statement to determine which operation to perform based on the operator entered by the user.