I am new to HDL and just wanted to confirm whether these lines of code are written in VHDL or Verilog?
DE0_SOPC DE0_SOPC_inst(
// 1) global signals:
.clk(CLOCK_50),
.pll_cpu(),
.pll_sdram(DRAM_CLK),
.reset_n(system_reset_n));
Yes. These are verilog code lines. As per your previous comments, Type: .v files belong to verilog codes.