Hallo Waleed,

assume you want to display 10 characters, each consisting of 5X7 matrix. Between every two characters there should be a space. So, you would need a 6X7 matrix per character and dispaly matrix consisting of 7 rows and 60 columns. You could use the following scheme, but keep in mind that only a small fraction of all needed components is shown, of course:





With lower HC574 you can decode 8 different HC238, resulting in 64 different columns. With upper HC574 you define which LEDs per column is turned-on.

Writing text to display works as following: Write LED code of first character and first column of 5X7 matrix into upper HC574, while not having any HC238 enabled. Then select first column of display by writing according address into lower HC574. Enable HC138 (and by this the according HC238) for about 100µsec.
Then, write LED code of first character and second column of 5X7 matrix into upper HC574, while not having any HC238 enabled. Then select second column of display by writing according address into lower HC574. Enable HC138 (and by this the according HC238) for about 100µsec.
And so on.

100µsec duration for each column of display gives 60 x 100µsec = 6msec for the whole display, gives an updating frequency of about 170Hz. So, according to Erik, no flickering should occur. There's even enough time to manipulate text, in order to achieve some certain 'text running' over display. The best moment for this is, when all columns just have been written. Then, eyes do not see any interruption. But look, that display updating frequency does not fall below about 100Hz. Ask Erik why... {grin}

About 50mA per LED should flow. That's the current which must be delivered by each PNP transistor. Choose a base current of about 5mA, then upper HC574 is able to drive all PNP transistors.
NPN transistors driven by HC238 must be able to deliver up to 7 x 50mA = 350mA. According base current for securely driving transistor is much too big for HC238. So, you should use here some Darlington transistor. There are nice arrays arround, doing the job quite well. But a solution using discretes only is also possible.

Have a look at datasheet of LED and find out what current they accept for short intervals. High efficiency LED would be highly recommended. But, of course, price can be much higher.

Good luck,
Kai