Sinc function doesnt look good

Hello so I have the code below :

clear all;
clc;
Fs = 100;
Ts = 1/Fs;

t=-1:Ts:1;

%u(t-0.5)
step = zeros(size(t));
step(t>0.5) = -1;

figure
grid
subplot(3,2,1)
plot(t,step)
title ('u(t-0.5)')

%u(t+0.5)
step2 = zeros(size(t));
step2(t>-0.5)= 1;

grid
subplot(3,2,2)
plot(t,step2)
title ('u(t+0.5)')

xt=step2+step;

dt = 1/100;

grid
subplot(3,1,3)
plot(t,xt)
title ('u(t+0.5)-u(t-0.5)')

y = conv(xt,xt)*dt;

t3 = -2 :Ts:2;

grid
figure
subplot(2,1,1)
plot(t3,y)
title('first convo')

z = conv (y,xt )*dt;

t4= -3:Ts:3;

dw=1/100;

grid
subplot(2,1,2)
plot(t4,z)
title('second convo')

q = conv(z,xt)*dt;
t5 = -4:Ts:4;

grid
figure
plot(t5,q)
title('third convo')

nfft1=length(xt)*32;
XT=fft(xt,nfft1)*dw;
XT=fftshift(XT);

F=-Fs/2:Fs/nfft1:Fs/2-Fs/nfft1;

grid
figure
plot(F,abs(XT));
title('xt in freq')

nfft2=length(y)*32;
Y = fft(y,nfft2)*dw;
Y = fftshift(Y);

F=-Fs/2:Fs/nfft2:Fs/2-Fs/nfft2;

grid
figure
plot(F,abs(Y))
title('first  convolution in freq')

nfft3=length(z)*32;
Z=fft(z,nfft3)*dw;
Z=fftshift(Z);

F=-Fs/2:Fs/nfft3:Fs/2-Fs/nfft3;

grid
figure
plot(F,abs(Z))
title('second convolution in freq')

nfft4=length(q)*32;
Q=fft(q,nfft4)*dw;
Q=fftshift(Q);

F=-Fs/2:Fs/nfft4:Fs/2-Fs/nfft4;

grid
figure
plot(F,abs(Q))
title('third convolution in freq')

XT is a sinc function as it turned out on paper but when I plot it it doesnt look like a sinc function . Is the code wrong or is it right and that's how it's supposed to look ?