Cumulative distribution of a uniform on an interval

Let $X$ be uniformly distributed on the interval $[a,b]$ with $a<b$. Write down its cumulative distribution function $F(x)=\mathbb{P}(X\le x)$ for every real $x$.

$F(x)=0$ for $x<a$, $\tfrac{x-a}{b-a}$ for $a\le x\le b$, and $1$ for $x>b$. The density is the constant $\tfrac1{b-a}$ on $[a,b]$, so the CDF rises linearly across the interval.