How to check if data is normally distributed

data= randn(100); %generate random normally distributed 100x100 matrix
ref1= randn(100); %generate random normally distributed 100x100 matrix
ref2= rand(100); %generate random uniformly distributed 100x100 matrix

x=sort(data(:));
y1=sort(ref1(:));
y2=sort(ref2(:));

subplot(1,2,1); plot(x,y1); 
subplot(1,2,2); plot(x,y2);

The first plot should be a straight line (indicating that the data distribution matches the reference distribution. The second plot isn't a straight line, indicating that the distributions do not match.