The ENIAC computer was an enormous machine that occupied about 1,800 square feet of floor space, arranged in a U-shape stretching up to 80 feet long along three walls. It stood approximately 8 feet tall and was about 2 to 3 feet deep, weighing over 27 to 30 tons. In terms of memory, the ENIAC initially had no internal memory storage like modern computers. Instead, it used 20 accumulators as a form of internal memory, each accumulator able to store ten digits. These accumulators used ten-position ring counters where each digit required 36 vacuum tubes. External memory was provided by punch cards for input and output. Later, in 1953, a 100-word magnetic-core memory was added to enhance its memory capacity, but originally its memory was quite limited by today's standards. Thus, the ENIAC was a very large and heavy machine with minimal memory capacity consisting mostly of accumulators and punch card storage initially.