function x = gen_fn(c)
    global sp ep sf bp t;
    %t=linspace(sp,ep,sf*(ep-sp)+1);
    clc;
    fprintf('Do you want to plot a continuous or a discrete signal ?\n');
    cd=lower(input('Your Choice : ','s'));
    if not(strcmp(cd,'continuous') || strcmp(cd,'discrete'))
        fprintf('Invalid Input !\n\n');
        x=-1;
        return;
    end

    switch c
        case 1
            %Here comes the code for Sinusoidal Plotting .
            %f=A*sin(2*pi*f*t+(ph*pi/180))
            fprintf('\nYour choice was Sinusoidal !\n\n');
            if bp
                sep=str2num(input('Enter this function''s end point ','s'));
                t=linspace(sp,sep,sf*(sep-sp)+1);
                bp=bp-1;
                sp=sep;
            end
            A=str2num(input('Amplitude : ','s'));
            ps=str2num(input('Phase Shift in degrees : ','s'));
            fq=str2num(input('Frequency : ','s'));
            f=A*sin(2*pi*fq*t+(ps*pi)/180);
            if strcmp(cd,'continuous')
                plot(t,f,'r');
            else
                stem(t,f,'r');
            end
            hold on;
        case 2
            %Here comes the code for DC Plotting .
           fprintf('\nYour choice was DC !\n\n');
            if bp
                sep=str2num(input('Enter this function''s end point ','s'));
                t=linspace(sp,sep,sf*(sep-sp)+1);
                bp=bp-1;
                sp=sep;
            end
            dcv=str2num(input('DC value : ','s'));
            x=linspace(sp,ep,sf*(ep-sp)+1);
            y=x*0;
            z=0;
            for i=linspace(sp,ep,sf*(ep-sp)+1);
                z=z+1;
                if (i==0) y(z:length(y))=1;break; end
            end
            if strcmp(cd,'continuous') plot(x,dcv*y);
            else stem(x,dcv*y); end
            axis();
            xlabel('t');
            ylabel('DC Function');
            hold on;
        case 3
            %Here comes the code for Ramp Plotting .
            fprintf('\nYour choice is Ramp !\n\n');
            if bp
                sep=str2num(input('Enter this function''s end point ','s'));
                t=linspace(sp,sep,sf*(sep-sp)+1);
                bp=bp-1;
                sp=sep;
            end
            slope=str2num(input('Ramp slope : ','s'));
            intrspt=str2num(input('Interception with Y-axix : ','s'));
            if strcmp(cd,'continuous') plot(t,slope*t+intrspt);
            else stem(t,slope*t+intrspt); end
            xlabel('t');
            ylabel('Ramp function');
            hold on;
        case 4
            %Here comes the code for Exponential Plotting .
            fprintf('\nYour choice was Exponential !\n\n');
            if bp
                sep=str2num(input('Enter this function''s end point ','s'));
                t=linspace(sp,sep,sf*(sep-sp)+1);
                bp=bp-1;
                sp=sep;
            end
            A=str2num(input('Amplitude : ','s'));
            ec=str2num(input('Exponential constant : ','s'));
            f=exp(ec*t);
            if strcmp(cd,'continuous')
                plot(t,f,'b');
            else
                stem(t,f,'b');
            end
            hold on;
        case 5
            %Here comes the code for impulse Plotting .
            fprintf('\nYour choice was Impulse !\n\n');
            if bp
                sep=str2num(input('Enter this function''s end point ','s'));
                t=linspace(sp,sep,sf*(sep-sp)+1);
                bp=bp-1;
                sp=sep;
            end
            loc=str2num(input('Impulse location : ','s'));
            if loc>ep||loc<sp
                fprintf('Wrond entry !');
                x=-1;return;
            end
            for i = 1 : length(t)
                if (t(i)==loc) x(i)=1;
                else x(i)=0;
                end
            end
            if strcmp(cd,'continuous')
                plot(t,x);
            else
                stem(t,x);
            end
            axis();
            xlabel('n');
            ylabel('Impulse Function');
            hold on;
        case 6
            %Here comes the code for Unit Step Plotting .
            fprintf('Your choice is Unit step Function\n\n');
            if bp
                sep=str2num(input('Enter this function''s end point ','s'));
                t=linspace(sp,sep,sf*(sep-sp)+1);
                bp=bp-1;
                sp=sep;
            end
            amp=str2num(input('Amplitude : ','s'));
            tl=str2num(input('Location of transition : ','s'));
            x=linspace(sp,ep,sf*(ep-sp)+1);
            y=x*0;
            z=0;
            for i=linspace(sp,ep,sf*(ep-sp)+1);
                z=z+1;
                if (i==tl) y(z:length(y))=1;break; end
            end
            if strcmp(cd,'continuous') plot(x,amp*y);
            else stem(x,amp*y); end
            axis();
            xlabel('t');
            ylabel('Unit Step Function');
            hold on;
        case 7
            %Here comes the code for Rectangular Plotting .
            fprintf('\nYour choice was Rectangular !\n\n');
            if bp
                sep=str2num(input('Enter this function''s end point ','s'));
                t=linspace(sp,sep,sf*(sep-sp)+1);
                bp=bp-1;
                sp=sep;
            end
            wids=(str2num(input('Rectangle Width : ','s'))/2);
            amp=str2num(input('Rectangle Amplitude : ','s'));
            center=str2num(input('Rectangle Center : ','s'));
            x=linspace(sp,ep,sf*(ep-sp)+1);
            %y=not((abs(x) <= (center-wids)) | ( abs(x) >= (center+wids)));
            y=not((x <= (center-wids)) | ( x >= (center+wids)));
            y=y*amp;
            if strcmp(cd,'continuous') plot(x,y);
            else stem(x,y); end
            xlabel('t');
            ylabel('Rectangular Function');
            hold on;
            %x=1;syms x;
            %if strcmp(cd,'continuous')
            %ezplot(A*rectangularPulse(-wid,wid,x-cor),[sp ep]);
        otherwise
            disp('Nothing to be done !')
    end
    hold on;
    x=0;
end
%HAMID'S FUNCTIONS :
%%%%%%%%%%%%%%%%%%%%
%fprintf('Your choice is Unit step Function\n\n');
%
%start_point=input('The start point is = ');
%end_point=input('The end point is = ');
%%%smpl_freq=input('The sampling frequancy is = ');
%amp=input('The Amplitude is :');
%trans_location=input('The location of transition is = ');
%
%t=[trans_location-abs(start_point):trans_location trans_location:abs(end_point)+trans_location] %%el zero mara bib2a sorto zero, w mara bib2a sorto 1 3shan nozbot el rasma fel plot
%q=[zeros(1,abs(start_point)+1) ones(1,abs(end_point)+1)]
%plot (t,amp*q);