数学符号exp是什么意思啊?

exp
函数名: exp
功 能: 指数函数
用 法: double exp(double x);
程序例:

#include <stdio.h>
#include <math.h>

int main(void)
{
double result;
double x = 4.0;

result = exp(x);
printf("'e' raised to the power \
of %lf (e ^ %lf) = %lf\n",
x, x, result);

return 0;
}